Bypass circuit and method to bypass power modules in power system

ABSTRACT

A method for a power system having a string of a plurality of power sources connected across a power device includes connecting a plurality of safe voltage units having safety switches connected respectively across each of the power sources. The method includes sensing a plurality of parameters of the power sources, and monitoring for a signal transmitted from the power device. Each of the safety switches is activated to be OFF responsive to detecting the signal within a predetermined time period. Upon not detecting the signal from the power device within the predetermined time period, a safe mode of operation of the power system is entered in which the voltages of each of the power sources is reduced to a voltage level less than a predetermined voltage level by turning the safety switches ON.

RELATED APPLICATIONS

This application is a continuation of application Ser. No. 15/998,858,filed Aug. 17, 2018, entitled “Bypass Circuit and Method to Bypass PowerModules in Power System”, which is a continuation in part of patentapplication Ser. No. 15/924,564, filed Mar. 19, 2018, entitled “BypassCircuit and Method to Bypass Power Modules in Power System”, whichclaims priority to provisional application Ser. No. 62/478,366, filedMar. 29, 2017, entitled “Bypass Circuit”, and to provisional applicationSer. No. 62/547,221, filed Aug. 18, 2017, entitled “Bypass of aPhotovoltaic Module”, the entire contents of which are incorporatedherein by reference for all purposes.

BACKGROUND

Power systems may have multiple power generators coupled to powerdevices. Power systems may be configured to control the power harvestingand extracting from the power generators, and in some embodiments,bypass one or more power generators and/or power devices. In somescenarios, the power system may operate more efficiently by bypassingone or more power devices. In some scenarios, one or more power devicesmay experience potentially unsafe conditions, such as over-heating orover-voltage. Safety regulations may require to disconnect, or bypassunsafe parts of the system. Safety regulations may require to loweringthe voltage or heat of a power system or power device or to distanceand/or electrically separate a high voltage point from a system powerdevice. One way to lower the voltage or to distance and/or separate thehigh voltage point from the system power device may be to bypass a powerdevice.

Also, bypass circuits, such as bypass diodes or free-wheeling diodes,may be wired in parallel across the outputs of intercoupled powersources such as photovoltaic (PV) panels, batteries or generators, toprovide a current path around them in the event that a power sourcebecomes faulty by failing to provide power on its output. For example,the use of bypass circuits with regard to intercoupled PV panels, mayallow a series string of coupled PV cells, PV panels and/or a seriesstring of serially connected power devices outputs to continue supplyingpower to a load at a reduced voltage rather than no power at all, sincethe use of bypass circuits may allow continued current draw around theoutput of a faulty PV panel output and/or power device. Certain bypasscircuits may incur significant losses (e.g., due to a substantialvoltage drop across a conducting bypass circuit). There is a need forefficient bypass circuits that may allow bypassing power sources and/orother circuit elements without incurring significant losses.

SUMMARY

The following summary is a short summary of some of the inventiveconcepts for illustrative purposes only, and is not intended to limit orconstrain the inventions and examples in the detailed description. Oneskilled in the art will recognize other novel combinations and featuresfrom the detailed description.

Illustrative embodiments disclosed herein may be with respect to powersources in a power system and may consider the interconnection ofvarious groups of power sources. Each group of power sources may containdifferent types of power derived from both renewable energy sources suchas provided from sunlight, wind or wave power, and non-renewable energysources such as fuel used to drive turbines or generators, for example.Some illustrative embodiments may consider the connection of DC sourcesto a load via multiple power modules.

Illustrative embodiments disclosed herein may include a power systemutilized to supply power to a load and/or a storage device. The powersystem may include various inter connections of groups of direct current(DC) power sources that also may be connected in various series,parallel, series parallel and parallel series combinations, for example.More specifically, illustrative embodiments disclosed herein include apower system that comprises a plurality of power sources connected in aseries string, wherein the series string is connected across a powerdevice to provide a voltage of the series string to the power device.The power system includes a plurality of safe voltage units eachincluding a respective plurality of safety switches connectable acrosseach one of the power sources and a plurality of sensors connectable toeach one of the power sources. The sensors are configured to sense aplurality of parameters of the power sources. Each of the safe voltageunits are configured to monitor for a signal output from the powerdevice. The power system is controllable such that at least one of: a)detection of the signal by the safe voltage units within a predeterminedtime period, and b) an operating criteria determined based on theparameters sensed, causes each of the safety switches to be OFF in anormal mode of operation of the power system. The power system iscontrollable such that, when at least one of the safe voltage units doesnot detect the signal within the predetermined time period, the powersystem enters into a safety mode of operation from the normal mode ofoperation. The power system is controllable such that, upon entry of thepower system into the safety mode of operation, the safety switches arecaused to be ON to ensure a voltage level at each point in the seriesstring to be at or below a predetermined voltage level, thereby reducingthe level of the voltage of the series string to beat or below thepredetermined voltage level.

According to some aspects of the power system, the power sourcescomprise batteries, wherein power from the power device is applied tothe series string to charge the batteries in the normal mode ofoperation, wherein at least one of the receiving of the signal andoperating criteria applied to the parameters sensed enables each of thesafety switches to be OFF or ON responsive to the normal mode ofoperation.

According to some aspects of the power system, the power sourcescomprise batteries, wherein power from the batteries is provided fromthe series string to the power device to thereby discharge the batteriesin the normal mode of operation, wherein at least one of the receivingof the signal and operating criteria applied to the parameters sensed,enables each of the safety switches to be OFF or ON, in the normal modeof operation of the power system.

According to some aspect of the power system, the power sources comprisephotovoltaic panels, wherein power from the photovoltaic panels isprovided from the series string to the power device in the normal modeof operation, wherein at least one of the receiving of the signal andoperating criteria applied to the parameters sensed, enables each of therespective safety switches to be OFF when the photovoltaic panels areunshaded or ON when photovoltaic panels are shaded, in the normal modeof operation.

According to some aspects of the power system, the voltage of the seriesstring is less than an open circuit voltage of the power sources.

According to some aspects of the power system, an operating power isprovided to the safety switches to cause the safety switches to be ON orOFF in the normal mode of operation of the power system, and whereinoperating power of the safe voltage units are supplied from at least oneof the power sources and an auxiliary source of power independent of thepower sources.

According to some aspects of the power system the operating criteria inthe normal mode is selected from the group of criteria comprising: thevoltage levels of the power sources, polarities of the power sourcesrelative to each other, current level in the series string, thedirection of the current in the series string or the voltage level ofthe series string.

According to some aspects of the power system, the power system entersinto the safety mode of operation from the normal mode of operation dueto at least one of: a disconnection in the series string, adisconnection between the series string and the power device, an outageof a grid connected to the power device, a leakage current, amalfunction of the power device, a trip of a circuit breaker or ashutdown of power device.

According to some aspects of the power system, the voltage of the seriesstring is the sum of each of the voltages of the power sources.

According to some aspects of the power system, the power system furtherincludes a load connected to the power device, wherein the load [isselected from the group of loads comprising: an AC grid, a DC grid, atransformer, a DC to AC inverter, a DC to DC converter, or an AC to DCrectifier.

Illustrative embodiments disclosed herein include a method for a powersystem having a series string of a plurality of power sources connectedacross a power device, in which the method includes connecting aplurality of safe voltage units including a plurality of safety switchesconnected respectively across each of the power sources. The method alsoincludes monitoring an operating power applied to the safety switches.The method further includes sensing a plurality of parameters of thepower sources. The method still further includes monitoring, by the safevoltage units, for a signal transmitted from the power device. Themethod also includes activating each of the safety switches to be OFFresponsive to detecting the signal within a predetermined time periodand at least one of the operating power and a sensing being associatedwith a normal mode of operation. The method further includes upon notdetecting the signal from the power device within the predetermined timeperiod, or based on the operating power applied to the safety switchesbeing associated with an abnormal mode of operation, entering a safemode of operation of the power system by reducing the voltages of eachof the power sources to a voltage level less than a predeterminedvoltage level by activating the safety switches to be ON.

According to some aspects of the method, the activating comprises:turning at least one of the safety switches from OFF to ON responsive tothe monitoring, wherein the monitoring monitors for a reverse polarityof a respective power source relative to the other polarities of theother power sources.

According to some aspects of the method, the reducing ensures a safevoltage level at each point in the series string of power sources.

According to some aspects of the method, a lowering of a voltage of theseries string is achieved by activating at least one of the safetyswitches to be ON, thereby reducing the voltage of the string to a safelevel of voltage in the safe mode of operation, wherein in the safe modeof operation, a voltage of the series string is less than an opencircuit voltage of each of the power sources, and wherein the operatingpower is selected from the group comprising: the voltage levels of thepower sources and the polarities of the power sources relative to eachother, the current level, and the direction of the current in the seriesstring or the voltage level of the series string.

According to some aspects of the method, the sensing includes sensing atleast one of: a disconnection in the series string, and a disconnectionbetween the series string and the power device.

As noted above, this Summary is merely a summary of some of the featuresdescribed herein. It is not exhaustive, and it is not to be a limitationon the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentdisclosure will become better understood with regard to the followingdescription, claims, and drawings. The present disclosure is illustratedby way of example, and not limited by, the accompanying figures.

FIG. 1A shows a power system, according to one or more illustrativeembodiments.

FIG. 1B illustrates circuitry that may be found in a power device suchas a power module, according to one or more illustrative embodiments.

FIG. 1C shows a buck+boost circuit implementation for a power converter,according to one or more illustrative embodiments.

FIG. 1D shows a buck circuit implementation for a power converter,according to one or more illustrative embodiments.

FIG. 1E shows a power system, according to one or more illustrativeembodiments.

FIG. 1F shows a power system, according to one or more illustrativeembodiments.

FIG. 1G is part block diagram, part schematic of a bypass circuit,according to one or more illustrative embodiments.

FIG. 1H shows a flowchart of a method, according to one or moreillustrative embodiments.

FIG. 1I shows further details of a coupling circuit, a bypass switch anda circuit in a bypass circuit, according to one or more illustrativeembodiments.

FIG. 1J shows further details of the circuit in the bypass circuit ofFIG. 1I, according to one or more illustrative embodiments.

FIG. 1K shows a flow chart of a method for a bypass circuit, accordingto one or more illustrative embodiments.

FIG. 1L shows transient traces of measurements made on a working designof the bypass circuit shown in FIG. 1I, according to one or moreillustrative embodiments.

FIG. 1M shows steady state measurement traces of a bypass circuit shownin FIG. 1I, according to one or more illustrative embodiments.

FIG. 1N shows steady state measurement traces of a bypass circuit,according to one or more illustrative embodiments.

FIG. 1O is a part circuit diagram, part schematic of a bypass circuit,according to one or more illustrative embodiments.

FIG. 1P is a part circuit diagram, part schematic of a bypass circuit,according to one or more illustrative embodiments.

FIG. 1Q shows further details of a bypass circuit, according to one ormore illustrative embodiments.

FIG. 1R shows a flow chart showing further details of a step shown inFIG. 1H, according to one or more illustrative embodiments.

FIG. 1S shows a power system, according to one or more illustrativeembodiments.

FIG. 1T is part schematic, part block diagram of a power systemincluding multiple power devices and multiple power generators,according to one or more illustrative embodiments.

FIG. 2 is a block diagram of a power device, according to one or moreillustrative embodiments.

FIGS. 2A and 2B are schematics of implementations of a bypass circuit,according to one or more illustrative embodiments.

FIG. 2C is a block diagram of part of a power device, according to oneor more illustrative embodiments.

FIG. 3 is a part schematic, part block diagram of a power device,according to one or more illustrative embodiments.

FIG. 3A is a part schematic, part block diagram of an auxiliary powercircuit connected to a bypass circuit, according to one or moreillustrative embodiments.

FIG. 3B is a part schematic, part block diagram of a power device,according to one or more illustrative embodiments.

FIG. 3C is a schematic of a bypass circuit, according to one or moreillustrative embodiments.

FIG. 4 is a part schematic, part block diagram of a power device,according to one or more illustrative embodiments.

FIG. 4A is a schematic diagram of selection circuit configured toactivate bypass, according to one or more illustrative embodiments.

FIG. 4B shows a flow chart of a method for activating a bypass switch,according to one or more illustrative embodiments.

FIG. 5 shows a flow chart of a method for operating a bypass circuit,according to one or more illustrative embodiments.

FIG. 6A illustrates a part schematic, part circuit diagram of a bypasscircuit, according to one or more illustrative embodiments.

FIG. 6B illustrates a part schematic, part circuit diagram of a circuitincluded in a bypass circuit, according to one or more illustrativeembodiments.

FIG. 6C illustrates a part schematic, part block diagram of a powerdevice, according to one or more illustrative embodiments.

FIG. 6D illustrates a part schematic, part block diagram of a powerdevice, according to one or more illustrative embodiments.

FIG. 7A is a part schematic, part block diagram of a power system,according to one or more illustrative embodiments.

FIG. 7B shows further details of a safe voltage unit which may belocated and connected to a power module, according to one or moreillustrative embodiments.

FIG. 7C shows a flow chart of a method applied in a power system forproviding safety, according to one or more illustrative embodiments.

FIG. 7D shows a flow chart of a method applied in a power system forproviding safety, according to one or more illustrative embodiments.

FIG. 7E shows a flow chart of a method applied in a power system forproviding safety, according to one or more illustrative embodiments.

FIG. 7F shows a power system, according to one or more illustrativeembodiments.

FIG. 7G shows further details of the power system of FIG. 7F, accordingto one or more illustrative embodiments.

DETAILED DESCRIPTION

In the following description of various illustrative embodiments,reference is made to the accompanying drawings, which form a parthereof, and in which is shown, by way of illustration, variousembodiments in which aspects of the disclosure may be practiced. It isto be understood that other embodiments may be utilized and structuraland functional modifications may be made, without departing from thescope of the present disclosure.

By way of introduction, features of one or more embodiments may bedirected to a power system and bypass circuits that may be utilized, forexample, on power module outputs in a series connection of the powermodule outputs. Each power module may have inputs coupled to one or moredirect current (DC) power sources. The series connection may be coupledacross a load. Possible features of bypass circuits disclosed herein mayinclude continuous bypass operation to provide a potential bypass ofserially coupled power module outputs and/or power source outputs. Insome embodiments, the bypass circuits may provide a bypass path during alow level of power production of an associated DC power source. In someembodiments, the bypass circuits may provide a bypass path when lowpower may be being produced on the output of at least one of the powermodules compared to other power module outputs. In some embodiments, thebypass circuits may utilize a switch, and may have low power losscompared to the use of other passive or active bypass devices, for bothhigh and low current flow through a series connection of power modulesand/or power sources. Illustrative bypass circuits may includeadditional circuitry that may be adapted to provide or increase a biasvoltage to the switch. The bias voltage may enable operation of theswitch below minimal operating parameters normally provided by a seriesconnection of the power modules and/or power sources outputs for theswitch.

The term “multiple” as used here in the detailed description indicatesthe property of having or involving several parts, elements, or members.The claim term “a plurality of” as used herein in the claims sectionfinds support in the description with use of the term “multiple” and/orother plural forms. Other plural forms may include for example regularnouns that form their plurals by adding either the letter ‘s’ or ‘es’ sothat the plural of converter is converters or the plural of switch isswitches for example.

The claim terms “comprise”, “comprises” and/or “comprising” as usedherein in the claims section finds support in the description with useof the terms “include”, “includes” and/or “including”.

Reference is made to FIG. 1A, which shows a power system 100 a,according to illustrative embodiments. Connection configuration 104 aincludes power source 101 with direct current (DC) output terminalscoupled to input terminals of power module 103. Connection configuration104 b includes two power sources 101 coupled in a series connection,with direct current (DC) output terminals of the series connectioncoupled to the input terminals of power module 103. The outputs of powermodules 103 may be coupled in series to form a series coupled string ofpower module 103 outputs. The series coupled string of power module 103outputs have a total voltage output Vstring that may be coupled acrossthe input of system power device 139. Power modules 103 may be a directcurrent (DC) to DC converter. Alternatively, total voltage outputVstring may be coupled across load 107. The outputs of power modules 103may be coupled in a series string to which more power modules 103 may beadded in order to provide the required input voltage (Vstring) to systempower device 139. System power device 139 may be, for example, a directcurrent (DC) to DC converter or may be DC to alternating current (AC)inverter supplying power to load 107. In some embodiments, system powerdevice 139 may be a combiner box for combining multiple strings of powersources, a safety device (e.g., a ground fault detector and/or or safetyswitch) and/or a monitoring device configured to measure, monitor and/orreport operational parameters associated with power system 100 a. Load107 may be, for example, a battery, an alternating current (AC) grid, aDC grid, or a DC to AC inverter.

A positive (+) output terminal of power module 103 in connectionconfiguration 104 a may be coupled to a negative (−) output terminal ofanother power module 103 or to a negative (−) output terminal of powermodule 103 in connection configuration 104 b. Bypass diodes BPD1 may beprovided with cathodes coupled to respective positive (+) outputterminals of power sources 101 and anodes coupled to respective negative(−) output terminals of power sources 101. Bypass diodes BPD1 may besimilarly coupled across the outputs of power modules 103. In connectionconfiguration 104 b two power sources 101 including their respectivebypass diodes BPD1 are connected in series to provide a voltage (V1+V2).The voltage (V1+V2) may then be applied to the input of a power module103 at terminals C and D of the power module 103. In connectionconfiguration 104 a, a single power source 101 with bypass diode BPD1provides a voltage V3. The voltage V3 is applied to the input of a powermodule 103 at terminals C and D of power module 103. Multiple outputs ofconnection configurations 104 a/104 b may be wired in series to give astring voltage (Vstring) that may be applied to the input of systempower device 139.

In the descriptions that follow, power sources 101 may be a photovoltaic(PV) generator, for example, a PV cell, a series string of PV cells, aparallel connection of serially coupled PV strings of PV cells, aphotovoltaic or solar panel, DC generator, a battery, or a fuel cell. Insome embodiments, for example where power source 101 includes multipleserially coupled power sources such as PV substrings or PV cells, bypassdiodes BPD1 may be replaced or complemented by additional diodes coupledin parallel to each serially coupled power source 101. DC sources ofpower for power sources 101 may also be derived from rectified orconverted sources of alternating current (AC) provided from a switchedmode power supply, dynamo or alternator, for example.

Operation of bypass diodes BPD1 may be illustrated, by way of example,where power sources 101 may be photovoltaic panels. A power source inconnection configuration 104 b is shown shaded with a shade 155. Assuch, the voltage V2 of the shaded power source 101 may have oppositepolarity with respect to the other unshaded panels with respect to theirvoltages V1 and V3. The opposite polarity may be as a result ofrestricted current flow of Ipanel so that the non-shaded panel mayattempt to push the current through power module 103. The attempt atpushing current flow may cause bypass diodes BPD1 to become forwardbiased. A function of bypass diodes BPD1 may therefore provide thefunction of bypassing a shaded panel and/or non-functioning power module103 output in a series string of serially connected power module outputs103. Without bypass diodes BPD1 on the outputs of power sources 101,voltage V2 may oppose the flow of current Ipanel so that current Ipanelmay be substantially zero. Substantially zero current Ipanel means thatpower module 103 in connection configuration 104 b may be inoperativeand therefore, both current Istring and voltage Vstring to the input ofsystem power device 139 may be substantially zero.

However, with bypass diodes BPD1, the opposite polarity of V2 may beapplied across the bypass diode BPD1 which forward biases bypass diodeBPD1. Voltages V1 and V3 may reverse bias the respective bypass diodesBPD1. The forward bias of V2 applied bypass diode BPD1 causes currentIpanel to flow from anode to cathode of bypass diode BPD1 at the outputof the shaded power source 101. Therefore, bypass diodes BPD1 provide apotential parallel path of current conduction around a panel or powersource 101 that is not working or is shaded with shade 155. In general,a working panel applies a reverse bias voltage across bypass diodes, anda non-working or shaded panel applies a forward bias voltage acrossbypass diodes BPD1.

Bypass diodes BPD1 may be coupled across the output of power modules103. If a power module 103 becomes inactive in a series string of powermodule outputs, current (Istring) attempting to pass through theinactive power module 103 may be offered an alternative, parallel path.The alternative, parallel path may be around the output of the inactivepower module 103 via bypass diode BPD1. Rather than a forcing of current(Istring) through an inactive power module 103 output, the flow ofcurrent (Istring) may cause bypass diode BPD1 to become forward biased.The forward biasing of bypass diode BPD1 may cause current Istring toflow from anode to cathode of bypass diode BPD1. Therefore, bypassdiodes BPD1 may provide a potential parallel path of current conductionaround a nonfunctioning power module 103 output in a series string ofcoupled power module 103 outputs.

Reference is now made to FIG. 1B, which illustrates circuitry that maybe found in a power device such as power module 103, according toillustrative embodiments. Power module 103 may be similar to or the sameas power module 103 shown in FIG. 1A. In some embodiments, power module103 may include power circuit 135. Power circuit 135 may include adirect current-direct current (DC/DC) converter such as a Buck, Boost,Buck/Boost, Buck+Boost, Cuk, Flyback and/or forward converter, or acharge pump. In some embodiments, power circuit 135 may include a directcurrent-alternating current (DC/AC) converter (also known as aninverter), such as a micro-inverter. Power circuit 135 may have twoinput terminals and two output terminals, which may be the same as theinput terminals and output terminals of power module 103. In someembodiments, power module 103 may include Maximum Power Point Tracking(MPPT) circuit 138, configured to extract increased power from a powersource the power device may be coupled to. In some embodiments, powercircuit 135 may include MPPT functionality. In some embodiments, MPPTcircuit 138 may implement impedance matching algorithms to extractincreased power from a power source the power device may be coupled topower module 103 may further include controller 105 such as amicroprocessor, Digital Signal Processor (DSP), Application-SpecificIntegrated Circuit (ASIC) and/or a Field Programmable Gate Array (FPGA).

Still referring to FIG. 1B, controller 105 may control and/orcommunicate with other elements of power module 103 over common bus 190.In some embodiments, power module 103 may include circuitry and/orsensors/sensor interfaces 125 configured to measure parameters directlyor receive measured parameters from coupled sensors and/or sensorinterfaces 125 configured to measure parameters on or near the powersource, such as the voltage and/or current output by the power sourceand/or the power output by the power source. In some embodiments, thepower source may be a photovoltaic (PV) generator including PV cells,and a sensor or sensor interface may directly measure or receivemeasurements of the irradiance received by the PV cells, and/or thetemperature on or near the PV generator.

Still referring to FIG. 1B, in some embodiments, power module 103 mayinclude communication interface 129, configured to transmit and/orreceive data and/or commands from other devices. Communication interface129 may communicate using Power Line Communication (PLC) technology,acoustic communications technology, or additional technologies such asZigBee™, Wi-Fi, Bluetooth™, cellular communication or other wirelessmethods. In some embodiments, power module 103 may include memory 123,for logging measurements taken by sensor(s)/sensor interfaces 125 tostore code, operational protocols or other operating information. Memory123 may be flash, Electrically Erasable Programmable Read-Only Memory(EEPROM), Random Access Memory (RAM), Solid State Devices (SSD) or othertypes of appropriate memory devices.

Still referring to FIG. 1B, in some embodiments, power module 103 mayinclude safety devices 160 (e.g., fuses, circuit breakers and ResidualCurrent Detectors). Safety devices 160 may be passive or active. Forexample, safety devices 160 may include one or more passive fusesdisposed within power module 103 where the element of the fuse may bedesigned to melt and disintegrate when excess current above the ratingof the fuse flows through it, to thereby disconnect part of power module103 so as to avoid damage. In some embodiments, safety devices 160 mayinclude active disconnect switches, configured to receive commands froma controller (e.g., controller 105, or an external controller) toshort-circuit and/or disconnect portions of power module 103, orconfigured to short-circuit and/or disconnect portions of power module103 in response to a measurement measured by a sensor (e.g., ameasurement measured or obtained by sensors/sensor interfaces 125). Insome embodiments, power module 103 may include auxiliary power circuit162, configured to receive power from a power source coupled to powermodule 103, and output power suitable for operating other circuitrycomponents (e.g., controller 105, communication interface 129, etc.).Communication, electrical coupling and/or data-sharing between thevarious components of power module 103 may be carried out over commonbus 190.

Reference is made to FIG. 1C, which shows a buck+boost circuitimplementation for power circuit 135, according to one or moreillustrative embodiments. The buck+boost circuit implementation forpower circuit 135 utilizes metal oxide semiconductor field effecttransistors (MOSFETs) for switches S1, S2, S3 and S4. The sources ofswitches S1, S2, S3 and S4 are referred to as first terminals, thedrains of S1, S2, S3 and S4 are referred to second terminals, and thegates of S1, S2, S3 and S4 are referred to as third terminals. CapacitorCin may be coupled in parallel across the respective positive (+) andnegative (−) input terminals C and D of the buck+boost circuit, wherethe voltage may be indicated as VIN. Capacitor Cout may be coupled inparallel across the respective positive (+) and negative (−) outputterminals A and B of the buck+boost circuit, where the voltage may beindicated as VOUT. First terminals of switches S3 and S2 may couple tothe common negative (−) output and input terminals of the buck+boostcircuit. A second terminal of switch S1 may couple to the positive (+)input terminal and a first terminal of switch S1 may couple to a secondterminal of switch S3. A second terminal of switch S4 may couple to thepositive (+) output terminal and a first terminal of switch S4 maycouple to the second terminals of switch S2. Inductor L1 may couplerespectively between the second terminals of switches S3 and S4. Thirdterminals of switches S1, S2, S3 and S4 may be operatively coupled tocontroller 105 (not shown in FIG. 1C).

Switches S1, S2, S3 and S4 may be implemented using semiconductordevices, for example, metal oxide semiconductor field effect transistors(MOSFETs), insulated gate bipolar transistors (IGBTs), bipolar junctiontransistors (BJTs), Darlington transistor, diode, silicon controlledrectifier (SCR), Diac, Triac or other semiconductor switches known inthe art. By way of example, switches S1, S2, S3 and S4 may beimplemented by use of bipolar junction transistors, where thecollectors, emitters and bases may refer to first terminals, secondterminals and third terminals described and defined above. Switches S1,S2, S3 and S4 may be implemented using mechanical switch contacts suchas hand operated switches or electro-mechanically operated switches suchas relays, for example. Similarly, implementation for power module 103may include, for example, a buck circuit, a boost circuit, a buck/boostcircuit, a Flyback circuit, a Forward circuit, a charge pump, a Cukconverter or any other circuit that may be utilized to convert power onthe input of power module 103 to the output of power module 103.

Power module 103 may include or be operatively attached to a maximumpower point tracking (MPPT) circuit (MPPT 138 for example). The MPPTcircuit may also be operatively coupled to controller 105 or anothercontroller 105 included in power module 103 that may be designated as aprimary controller. A primary controller in power module 103 maycommunicatively control one or more other power modules 103 that mayinclude controllers known as secondary controllers. Once aprimary/secondary relationship is established, a direction of controlmay be from the primary controller to the secondary controllers. TheMPPT circuit under control of a primary and/or central controller 105may be utilized to increase power extraction from power sources 101and/or to control voltage and/or current supplied to load 107.

Reference is made to FIG. 1D, which shows a buck circuit implementationfor power circuit 135, according to one or more illustrativeembodiments. The buck circuit implementation for power circuit 135utilizes metal oxide semiconductor field effect transistors (MOSFETs)for switches S1 and S3. The sources of switches S1 and S3 are referredto as first terminals, the drains of S1 and S3 are referred to secondterminals, and the gates of S1 and S3 are referred to as thirdterminals. Capacitor Cin may be coupled in parallel across therespective positive (+) and negative (−) input terminals C and D of thebuck circuit, where the voltage may be indicated as VIN. Outputterminals A and B of the buck circuit may be indicated as having anoutput voltage VOUT. A first terminal of switch S3 may couple to thecommon negative (−) output and input terminals of the buck circuit. Asecond terminal of switch S1 may couple to the positive (+) inputterminal, and a first terminal of switch S1 may couple to a secondterminal of switch S3. Inductor L1 may couple respectively between thesecond terminal of switches S3 and terminal A. Third terminals ofswitches S1 and S3 may be operatively coupled to controller 105 (notshown in FIG. 1D).

Reference is now made to FIG. 1E, which shows a power system 100,according to illustrative embodiments. Power harvesting system 100 maybe similar to power harvesting system 100 a but might not include bypassdiodes BPD1. Instead of or in addition to bypass diodes BPD1, bypasscircuits 115 having terminals A and B may couple across the outputterminals of power modules 103. Bypass circuit 115 provides a switchbetween terminals A and B, so that when the switch is ON a substantiallyshort circuit exists between terminals A and B, and when the switch isOFF a substantially open circuit exists between terminals A and B.Bypass circuits 115, in accordance with illustrative embodimentsdisclosed herein, may provide certain advantages when compared topassive bypass diodes (e.g. BPD1).

Reference is made to FIG. 1F, which shows a power system 100 b,according to illustrative embodiments. Multiple strings of seriallyconnected connection configurations 104 a and 104 b are shown in FIG.1E. The strings are connected in parallel across the input of systempower device 139, with voltage input to system power device 139 shown asVstring. System power device 139 may be a direct current (DC) to DCconverter or may be a DC to alternating current (AC) inverter supplyingpower to load 107. Power harvesting system 100 b may be similar to powerharvesting system 100 but might not include bypass diodes BPD1. Insteadof or in addition to bypass diodes BPD1, bypass circuits 115 havingterminals A and B may be implemented in connection configurations 104 aand 104 b as shown in FIG. 1E. In general, any number of connectioncombinations of multiple connection configurations 104 a/104 b mayinclude DC power sources 101 of differing types so that one connectionconfiguration has photovoltaic panels, for example, while anotherconnection configuration has wind powered DC generators.

Reference is now made to FIG. 1G, which is part schematic, part blockdiagram of bypass circuit 115, according to illustrative embodiments. Anoutput of a circuit 111 may couple to a coupling circuit 120 by couplingunit 120 a. Coupling unit 120 a may be a part of coupling circuit 120, apart of the output of circuit 111 and/or portions of both couplingcircuit 120 and circuit 111. Coupling unit 120 a may allow a coupling toprovide a feedback path via a circuit between the output of circuit 111and coupling circuit 120. The coupling may be a direct electricalconnection and/or coupling circuitry between the output of circuit 111and coupling circuit 120. The coupling may alternatively be a capacitivecoupling between the output of circuit 111 and coupling circuit 120. Thecoupling may alternatively be an inductive coupling between the outputof circuit 111 and coupling circuit 120. The inductive coupling mayinclude a mutual inductive coupling between two inductors that mayinclude a common direct electrical connection point shared between thetwo inductors. The inductive coupling may alternatively have twoinductors that are both wound on a core. The core may allow atransformer coupling arrangement between the two inductors whereby acommon direct electrical connection point is not shared between the twoinductors.

The output of coupling circuit 120 may couple to the input of switchBP1. The output of coupling circuit 120 may be such that switch BP1 maybe either ON or OFF. The poles of switch BP1 may couple to terminals Aand B, which may also be coupled across the input of circuit 111.Terminals A and B may also couple across output terminals of a powermodule 103 (not explicitly shown). When switch BP1 is ON; the powermodule 103 might be not functioning and string current Istring may flowthrough switch BP1. When switch BP1 is OFF; the power module 103 may befunctioning and string current Istring may flow through the output ofthe power module 103. Switch BP1 is shown as a MOSFET where a diode PD1is coupled across the drain and source of the MOSFET. Diode PD1 may bean intrinsic part of the MOSFET as a result of a structure of theMOSFET. The structure of the MOSFET may have an intrinsic p-n junction(diode) coupled between the drain and source. The intrinsic p-n junction(diode) of a MOSFET may be referred to as a body diode or a parasiticdiode. Other semiconductor devices may be used for switch BP1 which donot have an intrinsic p-n junction (diode) between terminals A and B, inwhich case a diode may be additionally coupled across terminals A and B.An additional switch wire C11 may connect between coupling circuit 120and circuit 111.

Switch BP1 may implemented using the switches that may already exist inpower circuit 135. With reference to FIG. 1C, which shows a buck+boostcircuit for power circuit 135, BP1 may implemented with the use ofswitches S2 and S4 across nodes A and B. Similarly, with reference toFIG. 1D, which shows a buck circuit for power circuit 135, switch BP1may implemented with the use of switch S3 across nodes A and B viainductor L1. In descriptions, which follow of the Figures, diodes showncoupled across a switch may be intrinsic to the switch or may beadditionally coupled across the switch.

Reference is now made again to FIG. 1G and to FIG. 1H, which shows aflow chart of a method 1000, according to illustrative embodiments. Theflow chart of method 1000 is used to explain the operation of the partschematic, part block diagram of bypass circuit 115 shown in FIG. 1G.The flow chart of method 1000 is also used to describe the operation ofinterconnected analog circuits that include coupling circuit 120, switchBP1 and circuit 111 in bypass circuit 115 described in greater detailbelow. As such, steps in method 1000 and indeed in steps of the othermethods described below might not preclude the use of digitalmethodologies such as use of a microprocessor or microcontroller andassociated algorithm to sense and control the operation of a bypassswitch that may include coupling to coupling circuit 120, switch BP1 andcircuit 111 in bypass circuit 115. Steps in method 1000 and indeed insteps of the other methods described below might not preclude the use ofany number of implementations that combines both analog and digitalmethodologies.

As such, steps of method 1000, methods described below and decisionsteps such as decision steps 1005 and 1009 in particular may be made byvirtue of a configuration of the analog circuits used below to implementcoupling circuit 120, switch BP1 and circuit 111 in bypass circuit 115.The configuration may include calculation and selection of componentvalues, types of components and the interconnections of components aspart of the circuit design of coupling circuit 120, switch BP1 andcircuit 111 in bypass circuit 115. The configuration may be basedtherefore, on the normal operating parameters where power sources 101and/or power modules 103 are functioning correctly or to accommodatenon-normal operating parameters of power systems 100 a/100 describedabove and in power systems described below. As such, the configurationwith respect to the decision aspect of the decision steps describedbelow may be responsive analog circuit wise to an event such as thebreakdown or failure of a power module 103 and/or power source 101 so asto provide a bypass of the power module 103 and/or power source 101. Inthis regard, the configuration with respect to bypass circuit 115 andthe other analog bypass circuit embodiments described below may beconsidered to be substantially activated and/or operated for most of thetime such that the steps of method 1000 are performed responsive to thecontinuously changing operating parameters of power systems 100 a/100.The continuously changing operating parameters of power systems 100a/100 for the bypass circuits 115 to be substantially activated most ofthe time may be where the power for the activation is provided from thestring of serial connected power module 103 outputs, a module 103 and/orpower source 101, a partial power from module 103 and/or power source101 or power is supplied from an auxiliary power source (for exampleauxiliary power from auxiliary power circuit 162). As such, bypasscircuit 115 and the other analog bypass circuit embodiments describedbelow when considered as being substantially activated most of the timemight not require sensors 125, controller 105 and associated algorithmto decide respectively in steps 1005/1007 to activate switch BP1 (ON) orto de-activate switch BP1 (OFF) in respective steps 1009/1011. A waytherefore to enable a de-activation of bypass circuit 115 and the otheranalog bypass circuit embodiments described below from beingsubstantially activated most of the time is for a controller to usedriver circuitry 170 to apply a voltage to the gate of switch BP1 sothat switch BP1 is OFF and/or de-activated thereby.

The configuration may also give the decision aspect of the decisionsteps described below so as to be responsive to an event such as a powermodule 103 and/or power source 101 reverting back to normal operation soas to remove a bypass of a power module 103 and/or power source 101.

The discussion that follows uses by way of non-limiting example, a powersystem such as power system 100 where power sources 101 are photovoltaicpanels coupled to the inputs of power modules 103, and where the outputsof power modules 103 are coupled in series. The description that followsreferences power modules 103 but may equally apply to power sources 101.The configuration in this regard may take into account the voltages andcurrents present in the string of serially connected power module 103outputs for example.

At step 1003, switch BP1 may be coupled across the outputs of a powermodule 103 where there may be a series string of power module 103outputs. Provided the power modules 103 are functioning properly, switchBP1 is inactive (OFF). Alternatively, switch BP1 may also be coupledacross the outputs of power sources 101.

At decision step 1005, a first bypass current conduction of diode PD1may be an indication of power module 103 and/or power source 101 notfunctioning correctly. The indication according to the configuration maycause the subsequent activation of switch BP1 (step 1007) to be ON sothat the output of a malfunctioning power module 103 is bypassed.Otherwise, switch BP1 remains OFF so that the bypass function of switchBP1 is inactive (step 1003).

A power module 103 not functioning correctly may be as a result of apanel becoming shaded or a component failure within power module 103 forexample. As such, the flow of current (Istring) through an inactivepower module 103 output may become restricted. As a result of restrictedcurrent flow, the voltage outputs of the other power modules 103 in thestring may attempt to push the current through their outputs and throughthe inactive power module 103 output. The attempt at pushing currentflow of current may be caused by an increase in voltage output of theother power modules 103, which may cause diode PD1 to become forwardbiased. Whereas when a normal operation of power module 103 exists,diode PD1 and the MOSFET of switch BP1 are reversed biased (the MOSFETis OFF). The forward biasing of diode PD1 may cause string currentIstring to flow from anode to cathode of diode PD1 in the first bypasscurrent conduction of diode PD1.

The first bypass current conduction of diode PD1 and forward voltagedrop of diode PD1 is applied to the input of circuit 111, which maycause the oscillation of circuit 111. The output oscillations of circuit111 may be fed back to the input of switch BP1 via coupling circuit 120.The output of coupling circuit 120 connects to the gate (g) of theMOSFET of switch BP1. The output of coupling circuit 120 applied to thegate of the MOSFET of switch BP1 may be sufficient to cause the MOSFETof switch BP1 to switch ON so that switch BP1 is activated at step 1007.

At decision step 1009, if inactive power module 103 remains inactive,then the MOSFET of switch BP1 remains ON so that switch BP1 remainsactivated at step 1007. However, when power module 103 starts to becomeactive, both the MOSFET and diode PD1 of switch BP1 become reversebiased. Power module 103 may become active because a panel coupled topower module may become unshaded, for example. The reverse bias voltagesof both the MOSFET and diode PD1 of switch BP1 applied to the input ofcircuit 111 at terminals A and B may cause the ceasing of theoscillations of circuit 111. The output oscillations of circuit 111ceasing fed back to the input of switch BP1 via coupling circuit 120 maybe sufficient to cause the MOSFET of switch BP1 to switch OFF, so thatswitch BP1 is de-activated at step 1011. The reduction of voltageapplied to the gate of the MOSFET may cause the MOSFET to turn OFF.Alternatively, sensors 125 under control of controller 105 or some othercontroller may sense the reverse bias voltages of both the MOSFET anddiode PD1 of switch BP1. As a result of the reverse biases being sensed,switch BP1 may be switched OFF and power from a driver circuitry may beallowed to be resupplied to the switches of power module 103 to allowpower module 103 to function as normal. With the power modules 103functioning normally, switch BP1 is now inactive (OFF) but still coupledat terminals A and B (step 1003).

Reference is now made to FIG. 1I, which shows further details ofcoupling circuit 120, switch BP1 and circuit 111 in bypass circuit 115,according to illustrative embodiments. Coupling circuit 120 may includebiasing and driver circuitry 170 that has an output coupled to a firstend of resistor R3 and a first end of resistor R4. The second end ofresistor R3 may couple to the cathode of diode D1, a first end ofcapacitor C3 and the gate (g) of switch Q3 via switch wire C11. A secondend of resistor R4 may couple to a second end of capacitor C3 andterminal B. The second end of capacitor C3 may couple to a first end ofinductor L3 and a second end of inductor L3 may couple to the anode ofdiode D1. The gate (g) of switch BP1 may couple to the first ends ofresistors R3 and R4. The drain (d) of switch BP1 may couple to thecathode of diode PD1 at terminal B to give a return connection RET1. Theanode of diode PD1 may couple to the source (s) of switch BP1, the anodeof diode BD2 that belongs to switch Q3 and the source (s) of switch Q3.The drain (d) of switch Q3 may couple the cathode of diode BD2 and afirst end of inductor L1 of circuit 111. Switch BP1 may be a metal oxidesemiconductor field effect transistor (MOSFET), which may include diodePD1 or which might not include diode. Similarly switches Q1, Q2 and Q3may be MOSFETs, which include a diode like diode BD2 or which might notinclude a diode.

In circuit 111, a second end of inductor L1 may couple to the drains (d)of switches Q1 and Q2. The sources (s) of Q1 and Q2 may be coupledtogether to give a return connection RET2. A first end of resistor R1may couple between the gate of switch Q1 and the source (s) of switchQ1. A first end of resistor R2 may couple between the gate of switch Q2and the source (s) of switch Q2. The gate (g) of switch Q1 may couple toa first end of capacitor C2. A second end of capacitor C2 may couple toa first end of inductor L2 and a first end of capacitor C1. A second endof inductor L2 may provide return connection RET3. A second end ofcapacitor C1 may couple to the gate of switch Q2. Return connectionsRET1, RET2 and RET3 may couple together to form a return path that maybe separate to terminal B at the source(s) of switch BP1. Separationbetween the return path and terminal B in bypass circuit 115, along withthe integration of bypass circuit 115 across the output of a powermodule 103, may be achieved by disposing switch Q3 and diode BD2 betweenterminal B and inductor L1. Switches BP1, Q2 and Q3 may be metal oxidesemiconductor field effect transistors (MOSFETs) and switch Q1 may be ajunction field effect transistor (JFET).

In some embodiments, inductors L1, L2 and L3 may be mutually coupled onthe same magnetic core. In effect, the coupling between inductor L1 toL2 and then inductor L2 to L3 provide a possible function of couplingunit 120 a shown in FIG. 1G, which allows a coupling between the outputof circuit 111 and coupling circuit 120. Therefore, the output ofcircuit 111 across inductor L1 may be coupled back to the input ofcoupling circuit 120 via the mutual inductance between inductor L1 andinductor L3 and also coupled to inductor L2 via the mutual couplingbetween inductor L1 and inductor L2. The mutual inductance betweeninductor L1 and inductor L2 and voltages induced into inductor L2 drivethe gates (g) of switches Q1 and Q2 via the coupling of respectivecapacitors C2 and C1. The mutual coupling between inductor L1 andinductors L2 and L3 may be such that inductors L2 and L3 have a greaternumber of turns across the common magnetic core than inductor L1 does,so the voltages induced into inductors L2 and L3 are greater by virtueof the transformer equations:

$\frac{VL1}{VL2} = {\frac{NL1}{NL2}\mspace{14mu}{and}}$$\frac{VL1}{VL3} = \frac{NL1}{NL3}$

Where VL1, VL2 and VL3 are the respective voltages of inductors L1, L2and L3, where NL1, NL2 and NL3 are the respective number of turns ofinductors L1, L2 and L3.

The greater voltages induced into inductors L2 and L3 by virtue of thegreater number of turns NL2 and NL3 may allow for operation of switchesBP1, Q1, Q2 and Q3, whereas without the greater voltages induced,switches BP1, Q1, Q2 and Q3 might not be able to operate otherwise.

Inductor L2 and capacitors C1 and C2 in circuit 111 function as aColpitts oscillator.

The frequency of oscillation given by:

$f_{o} = \frac{1}{2\pi\sqrt{L_{2}\left( \frac{C_{1}C_{2}}{C_{1} + C_{2}} \right)}}$

Inductors L1, L2, L3, capacitors C1 and C2 may be chosen so that afrequency of oscillation for circuit 111 may be between 1 and 4Kilohertz (KHz). The low frequency of oscillation of circuit 111 maytherefore, provide low losses in the switching of Q1, Q2 and Q3.Alternatively, capacitor C1 may be replaced with another inductor sothat circuit 111 may be implemented as a Hartley oscillator. Inductor L3of coupling circuit 120 may be built on the same core as inductors L1and L2 in circuit 111, diode D1 may be used to rectify voltages inducedon inductor L3 that may be by virtue of the mutual coupling betweeninductor L3 to inductors L1 and L2 of circuit 111. The rectified pulsesmay drive the voltage (Vgs) between gate (g) and source (s) of theMOSFET of switch BP1 to turn switch BP1 ON for continuous conduction ofswitch BP1 at step 1007.

Reference is now made again to FIG. 1F with method 1000 applied to thefurther details of coupling circuit 120, switch BP1 and circuit 111 inbypass circuit 115 shown in FIG. 1G, according to illustrativeembodiments. At step 1003, switch BP1 may be coupled across the outputsof a power module 103 where there may be a series string of power module103 outputs. Switch BP1 is not active in step 1003.

At decision step 1005, specifically a first bypass current conduction ofdiode PD1 may be an indication of power module 103 and/or power source101 not functioning correctly. Consequently, the flow of current(Istring) through an inactive power module 103 output may becomerestricted. As a result of restricted current flow, the voltage outputsof the other power modules 103 in the string may attempt to push thecurrent through their outputs and through the inactive power module 103output. The attempt at pushing current flow of current may be caused byan increase in voltage output of the other power modules 103, which maycause diode PD1 to become forward biased so that a first bypass currentconduction of current occurs through diode PD1. Diode PD1 becomingforward bias also results in diode BD2 also being forward biased. Theforward biasing of diode BD2 allows the utilization of circuit 111 toinitiate a continuous operation of switch BP1. Detailed description ofthe operation of circuit 111 is described later on in the descriptionswhich follow.

At step 1007, circuit 111 may initiate the continuous operation ofswitch BP1. As soon as diode PD1 conducts, Q2 and/or Q1 may be ON, andcircuit 111 may maintain the continuous operation of switch BP1 so thatthe MOSFET of switch BP1 is ON such that the voltage (Vds) between drain(d) and source (s) of switch BP1 remains low, e.g., from about 10millivolts (mV) substantially up to 200 mV. A comparison between Vds of10 mV of switch BP1 and a forward voltage drop 0.7V of a bypass diode tobypass a string current Istring of 25 Amperes gives bypass power lossesof 0.25 Watts and 17.5 Watts, respectively. As such, operation of switchBP1 in bypass circuit 115 and other bypass circuit embodiments describedbelow provide efficient bypass circuits that may allow the bypassingpower sources and/or other circuit elements without incurringsignificant losses by the bypass itself. Bypassing power sources and/orother circuit elements without incurring significant losses may besignificant when compared to other ways of providing a bypass that mayinclude the use of bypass diodes, for example.

At step 1007, return connections RET1, RET2 and RET3 may couple togetherto form a return path that may be a separate return path to thatprovided at terminal B at the source (s) of switch BP1. Separationbetween the return path and terminal B between coupling circuit 120 andcircuit 111 may be by switch Q3 and diode BD2. Consequently,oscillations of circuit 111 may build on the drains of switches Q2and/or Q1, while the return path for the oscillations may be provided onthe sources(s) of switches Q2 and/or Q1.

At decision step 1009, if inactive power module 103 remains inactive,then the MOSFET of switch BP1 remains ON so that switch BP1 remainsactivated at step 1007. At decision step 1009, if switch BP1 remainsactivated at step 1007, power from driver circuitry 170 may be isolatedfrom being supplied to the inactive power module 103. However, whenpower module 103 starts to become active, for example when a panelbecomes unshaded that may be sensed by sensors 125, power from drivercircuitry 170 may be allowed to be resupplied to the switches of powermodule 103 to allow the functioning of power module 103. Both the MOSFETand diode PD1 of switch BP1 and diode BD2 at this point may becomereverse biased. The reverse bias voltages of both the MOSFET and diodePD1 of switch BP1 applied to the input of circuit 111 at the anode ofdiode BD2 may cause the ceasing of the oscillations of circuit 111. Theoutput oscillations of circuit 111 ceasing when feedback to the input ofswitch BP1 via coupling circuit 120 may be sufficient to cause theMOSFET of switch BP1 to switch OFF, so that switch BP1 is de-activatedat step 1011. Alternatively, sensors 125 under control of controller 105or some other controller may sense the reverse bias voltages of both theMOSFET and diode PD1 of switch BP1. As a result of the reverse biasesbeing sensed, switch BP1 may be switched OFF and power from drivercircuitry 170 may be allowed to be resupplied to the switches of powermodule 103 to allow power module 103 to function as normal. Thereduction of voltage applied to the gate of the MOSFET of switch BP1causes the MOSFET to turn OFF. With the power modules 103 functioningnormally switch BP1 is now inactive (OFF) but still coupled at terminalsA and B (step 1003).

Operation of Circuit 111

Reference is now made to FIG. 1J and FIG. 1K which show, respectively,circuit 111 and a flow chart of step 1007 in greater detail, accordingto illustrative embodiments. Step 1007 occurs if a power module 103 doesnot work, so that switch BP1 draws the current in the series string(Istring) in a path around the output of an inactive power module 103.Circuit 111 may be the same as described with regard to FIG. 1G, and maybe coupled to bypass switch BP1. Switches Q1 and Q2 may be biased withresistors R1 and R2 respectively. In operation of circuit 111 whenswitch BP1 is OFF and a power module 103 is working correctly at step1011, switch Q3 and diode BD2 may block leakage current through bypassswitch BP1 and block reverse voltage across bypass switch BP1 when thevoltage at terminal A may be much greater than the voltage at terminalB. Conversely when a power module 103 is not working at step 1007,switch Q3 is operated by the rectified output provided by diode D1 sothat diode BD2 is bypassed by switch Q3 when switch Q3 may be ON. SwitchQ3 OFF during step 1007 provides a block of leakage current throughbypass switch BP1. Switch Q3 being ON may additionally compensate forany drop in voltage across terminals A and B as a result of switch BP1being turned ON and being maintained as ON during step 1007 so as togive headroom for circuit 111 to oscillate. Switch Q3 and its operationis ignored and is to be considered to be ON, in order to simplify thefollowing description.

In decision step 1203, if a low amount of power is being produced by apower source 101 and respective power module 103 compared to other powersources 101 and respective power modules 103 in a series string of powermodule 103 outputs, a first bypass current conduction may therefore bethrough diode PD1. Similarly, if the power source 101 and respectivepower module 103 has a failure the first bypass current conduction mayalso be through diode PD1.

At decision step 1205 the first bypass current conduction may induce avoltage VL1 across inductor L1 since diode BD2 is similarly forwardbiased as diode PD1. At step 1205, bypass switch BP1 may be positivelybiased with respect to output voltage (VAB) of power module 103. Bypassswitch BP1 being positively biased with respect to output voltage (VAB)of power module 103 may be a result of power module 103 not functioning.The first bypass current conduction to provide the bypass of currentthrough bypass switch BP1 may therefore be through diode PD1, followedby the conduction of inductor L1 via diode BD2 and then by theconduction of inductor L1 by use of switch Q1 in a first stage ofoperation of bypass switch BP1.

An example of the low amount of power may be when power sources 101 maybe photovoltaic panels that have just begun to be illuminated (e.g., atdawn) or when a photovoltaic panel may be substantially and/or partiallyshaded. Shading may reduce power generated by a power source 101 (e.g.,reducing the power generated by, for example, 20%, 50% or even close to100% of the power generated by an unshaded power source). If enoughpower may be produced by power sources 101 in decision step 1203,circuit 111 may continue to oscillate with an initial use of switch Q1for a number of times according to the steps of 1209-1217 describedbelow as part of the first stage of operation of switch BP1 until thesecond stage of operation where switch Q2 and/or Q1 are used. Q1 may beimplemented using a junction field effect transistor (JFET) rather thana MOSFET since a JFET compared to a MOSFET may have a lower bias inputcurrent compared to a MOSFET and a JFET may conduct between source (s)and drain (d) when the voltage between gate (g) and source (Vgs) issubstantially zero. Q1 may also be implemented using a depletion modeFET.

Following on from the first stage with the use of Q1, steps 1209-1217are implemented with the use of switch Q2 and/or switch Q1 as part of asecond stage of operation of switch BP1. The principal of operation forboth the first stage and the second stage is that inductor L1 ismutually coupled to inductors L3 and L2 when current flows throughinductor L1. The mutual coupling is such that when current flows throughinductor L1, current flows in inductor L2 and induces a voltage VL2 intoinductor L2. Voltage VL2 may charge the gate (g) of switches Q2 and/orswitch Q1 (step 1209) via capacitors C1 and/or C2. The charging of thegate (g) of Q2 and/or switch Q1 may cause switch Q2 and/or switch Q1 tostart to conduct current between source (s) and drain (d) of switch Q2and/or switch Q1 so that Q2 and/or switch Q1 is ON (step 1211) for atime period ton.

The energy induced into inductor L1 during ton may be discharged by atime constant τ[L1]τ[L1]=L1×Req

where Req may be the equivalent resistance that includes resistors R2and/or R1 and the respective resistances (Rds) between drain (d) andsource (s) when switch Q2 and/or Q1 may be ON. The value of respectiveresistances (Rds) between drain (d) and source (s) when switch Q2 and/orQ1 may be ON may be derived from manufacturer data sheets for theparticular devices chosen for switches Q2 and Q1 as part of the designof circuit 111. Discharge of inductor L1 (step 1213) may continue indecision step 1215 until voltage VL2 of inductor L2 in decision step1215 drops below the threshold voltage of Q2 and/or switch Q1 whichmakes Q2 and/or switch Q1 switch OFF (step 1217) for a time period toff.Q2 and/or switch Q1 drain (d) voltage then may begin to increase by theratio:

$\frac{ton}{{toff} \times {VAB}}$

so that voltage may again increase on L2 for a time defined by a timeconstant τ[L2], after which switch Q2 and/or switch Q1 conducts again(step 1209), which may create the oscillation of circuit 111. The timeconstant τ[L2] may be given by:τ[L2]=√{square root over (L2×Ceq)}

where Ceq may be the equivalent capacitance that includes capacitors C1and C2 and the parasitic capacitances of switches Q2 and/or Q1.Parasitic capacitances of switches Q2 and/or Q1 may be derived frommanufacturer data sheets for the particular devices chosen for switchesQ2 and Q1 as part of the design of circuit 111. Parasitic capacitancesof switches Q2 and/or Q1 may or might not be a significant factor in thedesired value of time constant τ[L2]. Inductor L1 coupled to inductor L3may cause a voltage to be induced in inductor L3 when current flowsthrough inductor L1. The voltage induced into inductor L3 may berectified by diode D1. The rectified voltage of diode D1 may be appliedto the gate (g) of bypass switch BP1 via bias resistors R3 and R4, whichmay turn bypass switch BP1 to be ON (step 1007).

Reference is now made to FIG. 1L, which shows transient traces 181 ofmeasurements made on a working design of bypass circuit 115, accordingto illustrative embodiments. Transient traces 181 show the effects ofswitch BP1 in a transition from being OFF to being ON. The transienttraces further show the entry into steady state condition where switchBP1 is ON at step 1007. The steady state condition may be where switchBP1 is ON at step 1007 and may be an example of an inherentstabilization of bypass circuit 115. The inherent stabilization ofbypass circuit 115 may be established during the second stage ofoperation of switch BP1 at step 1007. The transition shows the effect ofthe operation of switch BP1: in the first bypass, current conductionthrough diode PD1, followed by switch Q1 being operated in the firststage of operation, followed by switch Q2 and/or switch Q1 beingoperated in the second stage of operation of switch BP1.

Trace 184 shows the transient behavior of the voltage (Vgs) between gate(g) and source (s) of the MOSFET of switch BP1. Trace portion 184 ashows when a power module 103 may be functioning incorrectly so thatswitch BP1 and/or diode PD1 are forward biased and string currentIstring flows through diode PD1. Trace portion 184 a is when a module103 and/power source 101 are not functioning correctly at step 1203.Trace portion 184 a shows how the gate (g) source (s) voltage Vgs ofswitch BP1 begins to fluctuate as a result of the first bypass currentconduction through diodes PD1 and BD2 at step 1205. Gate (g) voltage ofthe MOSFET of switch BP1 is derived from the rectified voltage (fromdiode D1) induced in inductor L3 which is mutually coupled to inductorL1. The rectified voltage (from diode D1) also drives the gate of switchQ3 so that after the first bypass current conduction of diodes PD1 andBD2 at step 1205, current flow through inductor L1 is through both thesource (s) and drain (d) of Q3 and/or diode BD2. Beyond trace portion184 a is shown the steady continued rise of the gate (g) source (s)voltage Vgs of switch BP1 of the first stage by use of switch Q1 andthen by the second stage by use of switches Q1 and/or Q2. Thefluctuation of gate (g) source (s) voltage (Vgs) of switch BP1 becauseof the first bypass current conduction through diodes PD1 and BD2 atstep 1205 and the use of switches Q1 and/or Q2 in steps 1209-1217 showsa steady buildup of Vgs during the first stage. As such, both theinitial fluctuation of Vgs and the steady buildup of Vgs during thefirst stage demonstrates a positive feedback loop between the output ofcircuit 111 back to the input of circuit 111 via coupling circuit 120.The positive feedback loop is therefore responsive to the output ofpower modules 103 and/or power sources 101 in order to establish thatVgs is sufficient to turn switch BP1 ON, to thereby provide a bypassacross terminals A and B.

Trace portion 180 shows the current flow of inductor L1. The principalof operation for the first bypass current conduction through diodes PD1and BD2, the first stage by use of switch Q1 and the second stage by useof switches Q1 and/or Q2 is that inductor L1 is mutually coupled toinductors L3 and L2 when current flows through inductor L1. The mutualcoupling is such that when current flows through inductor L1, currentflows in inductor L2 and induces a voltage VL2 into inductor L2. VoltageVL2 may charge the gates (g) of switches Q2 and/or switch Q1 (step 1209)via capacitors C1 and/or C2. The charging of the gate (g) of Q2 and/orswitch Q1 may cause switch Q2 and/or switch Q1 to start to conductcurrent between source (s) and drain (d) of switch Q2 and/or switch Q1so that Q2 and/or switch Q1 is ON (step 1211) for a time period ton.Discharge of inductor L1 (step 1213) may continue in decision step 1215until voltage VL2 of inductor L2 in decision step 1215 drops below thethreshold voltage of Q2 and/or switch Q1 which makes Q2 and/or switch Q1switch OFF (step 1217) for a time period toff. The transient nature ofthe ON and OFF periods, ton and toff for switches Q1 and/or switch Q2are shown by trace portion 180. The steady state at step 1007 for traces180 and 184 are shown in the descriptions of the figures that follow.

Inherent stabilization of bypass circuit 115 may be established duringthe second stage of operation of switch BP1 by virtue of the feedbackloop established from the output of circuit 111 back to the input ofcircuit 111 via coupling circuit 120 being responsive to the output ofpower modules 103 and/or power sources 101. As such, the steadycontinued rise of the gate (g) source (s) voltage Vgs of switch BP1 isonly allowed to rise to a certain level of voltage so as to maintainswitch BP1 to be ON. The feedback loop during the second stage thereforeis a negative feedback loop. The negative feedback loop may beresponsive to the output of power modules 103 and/or power sources 101establishes and maintains the activation of switch BP1 to be ONcontinuously at step 1007 until a power module 103 and/or power source103 becomes active once more at step 1009. Switch BP1 at step 1007 isforward biased with respect to terminals A and B during bypass mode andthe voltage applied to gate (g) of switch BP1 is such that switch BP1 iscontinuously ON for the time period that the non-functioning powermodule 103 is required to be bypassed. Likewise, the feedback loopresponsive to the output of power modules 103 and/or power sources 101establishes and maintains the deactivation of switch BP1 to be OFFcontinuously at step 1011 until a power module 103 and/or power source103 becomes once again inactive. Switch BP1 is reverse biased withrespect to terminals A and B during non-bypass mode and the voltageapplied to gate (g) of switch BP1 is such that switch BP1 iscontinuously OFF for the time period that the functioning power module103 is required not to be bypassed at step 1011.

Inherent stabilization may therefore occur when switch BP1 may be ON atstep 1007, so that as its drain to source voltage Vds falls, the gate(g) to source (s) voltage Vgs also falls. Similarly, stabilization ofbypass circuit 115 may be established when switch BP1 may be OFF at step1011, so that as its drain (d) to source (s) voltage Vds rises, the gate(g) to source (s) voltage Vgs also rises.

Reference is now made to FIGS. 1M and 1N, which show steady statemeasurement traces 182 and 180 made on bypass circuit 115, according toillustrative embodiments. The measurement traces shown are for when anon-functioning power module 103 as part of a series connection of powermodules 103 outputs is not functioning correctly and needs to bebypassed by switch BP1 for a string current (Istring) operating up to amaximum of 25 Amperes. The measurement traces demonstrate that switchBP1 is forward biased with respect to terminals A and B during bypassmode and the gate (g) of switch BP1 is such that switch BP1 iscontinuously ON for the time period that the non-functioning powermodule 103 is required to be bypassed.

Reference is now made to FIG. 1M, which shows an oscilloscope trace 182of the measured steady state traces 184, 186 and 188, according toillustrative embodiments. Trace 184 may be the measured gate (g) source(s) voltage Vgs of switch BP1 when switch BP1 is used to bypass a powermodule 103 output (step 1007) when a power module 103 does not work.According to trace 184, it can be seen that the measured gate (g) source(s) voltage Vgs of switch BP1 may stay substantially constant atapproximately 5.8 volts, which makes bypass switch BP1 to be ON for thetime periods ton and toff. Time periods ton and toff refer respectivelyto when switches Q2 and/or Q1 are ON (step 1211) and OFF (step 1217).Trace 186 shows the measured voltage across inductor L3 which begins atabout minus 1.3 volts, rises to a peak of approximately 13 volts,rapidly drops to minus 7.8 volts and then returns back to minus 1.3volts for a time period of toff (step 1217). The voltage across inductorL3 then remains at about minus 1.3 volts for a time period ton (step1211). Trace 188 is the measured voltage between drain (d) source (s)voltage Vds of switch Q2, which begins at minus 1.3 volts and rises to apeak of approximately 3.8 volts and returns back to minus 1.3 volts fora period of toff (step 1217). Vds then remains at minus 1.3 volts fortime period ton (step 1211).

Reference is now made to FIG. 1N, which shows an oscilloscope trace 180of the measured steady state current in inductor L1, according toillustrative embodiments. The steady state current in inductor L1 is forwhen switch BP1 is activated to be ON (step 1007). The ramp portion 180a of trace 180 begins at a current level through inductor L1 beginningat −350 micro-Amperes (μA) and carries on increasing for a time periodton (step 1211) where the current may reach 77 milli-Amperes (mA). Oncethe current in inductor L1 reaches 77 mA, the ramp drops back down to−350 μA for a time period toff (step 1217). At the end of the timeperiod toff (step 1217), the ramp portion 180 a of trace 180 begins onceagain where the current through inductor L1 reaches 77 mA for the timeperiod ton (step 1211). For both FIGS. 1L and 1M ton (step 1211) may be240 μseconds and toff may be 20 μseconds. The frequency of oscillationof circuit 111 may be the inverse of 260 μseconds which may be 3.85KiloHertz (KHz).

Utilization of a first bypass current conduction through diode PD1,switch Q1 in the first stage of operation, Q2 and/or Q1 in the secondstage of switch BP1 may therefore give a continuous operation of abypass of the output of a non-functioning power module 103. Thecontinuous operation of bypass switch BP1 to carry a wide range ofcurrents (e.g. substantially zero to 30 amperes of string current(Istring)) where the conduction of the bypass circuit 115 may be, forexample, 10 mV-200 mV compared to 0.7V of bypass diode BPD1.Additionally, operation of bypass circuit 115 may be utilized as part ofa ‘wake-up’ of power system 100 when power sources 101 (e.g.,photovoltaic (PV) generators) begin to produce a partial power or whenPV generators may be completely shaded. Bypass circuit 115 may thenutilize power from auxiliary power circuit 162 and/or the conduction ofdiode PD1 at step 1205 followed by the first and second stages ofoperation of bypass 115 as described above in steps 1209-1217 to bypassa power source and/or a PV generator.

Reference is now made to FIG. 1O, which shows a bypass circuit 115 a,according to illustrative embodiments. The sources (s) of switchesdescribed herein are referred to as first terminals, the drains (d) arereferred to second terminals and the gates (g) are referred to as thirdterminals. An output of charge pump 130 may be coupled to the input ofswitch BP1 across the first terminal and third terminal of switch BP1.The first and second terminals of switch BP1 connect to the input ofcharge pump 130. The anode of diode PD1 connects to the first terminalof switch BP1 and the cathode of diode PD1 connects to the secondterminal of switch BP1. Nodes A and B are provided respectfully at thesecond and first terminals of switch BP1. Charge pump 130 may beconfigured to receive a very low voltage (e.g., tens or hundreds ofmillivolts) at its input, and output a substantially larger voltage(e.g., several volts). To enable the substantially larger voltage,charge pump 130 may include several conversion stages. Variations ofillustrative circuits for charge pump 130 may be found in “0.18-V InputCharge Pump with Forward Body Biasing in Startup Circuit using 65 nmCMOS” (P. H. Chen et. al., ©IEEE 2010), “Low voltage integrated chargepump circuits for energy harvesting applications” (W. P. M. RandhikaPathirana, 2014), which may be used as or as part of charge pump 130.

Reference is now made to FIG. 1P, which shows a bypass circuit 115 b,according to illustrative embodiments. Bypass circuit is the same asbypass circuit 115 a but with a first terminal of switch Q3 connected toterminal B and a second terminal connected to the input of charge pump130. The third terminal of switch Q3 connects to the third terminal ofswitch BP1.

Reference is now made again to method 1000 shown in FIG. 1H and to FIGS.1O and 1P, according to illustrative embodiments. At step 1003, switchBP1 may be coupled across the outputs of a power module 103 where theremay be a series string of power module 103 outputs. Provided the powermodules 103 are functioning properly, switch BP1 is inactive (OFF).Alternatively, switch BP1 may also be coupled across the outputs ofpower sources 101.

At decision step 1005, a first bypass current conduction of diode PD1may be an indication of power module 103 and/or power source 101 notfunctioning correctly. The indication according to the configuration maycause the subsequent activation of switch BP1 (step 1007) to be ON sothat the output of a malfunctioning power module 103 is bypassed.Otherwise, switch BP1 remains OFF so that the bypass function of switchBP1 is inactive (step 1003). Whereas when a normal operation of powermodule 103 exists, diode PD1 and the MOSFET of switch BP1 are reversedbiased (the MOSFET is OFF). The forward biasing of diode PD1 may causecurrent Istring to flow from anode to cathode of diode PD1 in a firstbypass current conduction of diode PD1.

The first bypass current conduction of diode PD1 and forward volt dropof diode PD1 is applied to the input of charge pump circuit 130, whichmay cause the buildup of the voltage output of charge pump circuit 130.The output voltage of charge pump circuit 130 may be fed back to theinput of switch BP1. The output voltage of charge pump circuit 130applied to the gate of the MOSFET of switch BP1 may be sufficient tocause the MOSFET of switch BP1 to switch ON so that switch BP1 isactivated at step 1007. Conversely, with respect to the use of bypasscircuit 115 b when a power module 103 is not working at step 1007,switch Q3 is operated by the output of charge pump 130 so that diode BD2is bypassed by switch Q3 when switch Q3 may be ON. Switch Q3 OFF duringstep 1007 provides a block of leakage current through bypass switch BP1.Switch Q3 being ON, additionally compensates for any drop-in voltageacross terminals A and B as a result of switch BP1 being turned ON andbeing maintained as ON during step 1007 so as to may be give headroomfor charge pump 130 to function.

At decision step 1009, if inactive power module 103 remains inactivethen the MOSFET of switch BP1 remains ON so that switch BP1 remainsactivated at step 1007. However, when power module 103 starts to becomeactive both the MOSFET and diode PD1 of switch BP1 become reversebiased. Power module 103 may become active because a panel coupled topower module may become un-shaded for example. The reverse bias voltagesof both the MOSFET and diode PD1 of switch BP1 applied to the input ofcharge pump circuit 130 at terminals A and B may cause the decreasing ofthe output voltage of charge pump circuit 130 and/or a reverse voltageoutput of charge pump circuit 130. The decreasing of the output voltageof charge pump circuit 130 and/or a reverse voltage output of chargepump circuit 130 applied to the gate (g) of switch BP1 may be sufficientto cause the MOSFET of switch BP1 to switch OFF so that switch BP1 isde-activated at step 1011. The reduction of voltage applied to the gateof the MOSFET therefore may cause the MOSFET to turn OFF. Alternatively,sensors 125 under control of controller 105 or some other controller maysense the reverse bias voltages of both the MOSFET and diode PD1 ofswitch BP1. As a result of the reverse biases being sensed, switch BP1may be switched OFF and power from driver circuitry such as drivercircuitry 170 for example, may be allowed to be resupplied to theswitches of power module 103 to allow power module 103 to function asnormal. With the power modules 103 functioning normally, switch BP1 isnow inactive (OFF) but still coupled at terminals A and B (step 1003).

Reference is now made to FIG. 1Q, which shows further details for abypass circuit 115 c, according to illustrative embodiments. Coupling120 circuit may include resistor R5, capacitor C4, resistor R6, diode D2and inductor L5. Resistor R5 may have a first end coupled to the gate(g) of switch BP1. Resistor R5 may have a second end coupled to terminalB. Capacitor C4 may be coupled across resistor R5. A first end ofcapacitor C4 may be coupled to terminal B and to a first end of inductorL5. A second end of inductor L5 may be coupled to the anode of diode D2.A second end of capacitor C4 may be coupled to one end of resistor R6. Asecond end of resistor R6 may be coupled to the cathode of diode D2.

The sources (s) of switches described herein are referred to as firstterminals, the drains (d) are referred to second terminals and the gates(g) are referred to as third terminals. Circuit 111 a may include thesecond terminals of switch BP1 may couple to the second terminals ofswitch Q4 and the cathode of diode PD1 of switch BP1. The anode of diodePD1 may couple to terminal B, the voltage (Vin1) input of charge pump130 and a first end of inductor L4. The second end of inductor L4 maycouple to the first terminals of switch Q4. The third terminals ofswitch Q4 may couple to the voltage output (Vout2) of PWM 132. Theoutput voltage (Vout1) of charge pump 130 may couple to the anode ofdiode D5. The cathode of diode D5 may couple to the cathode of diode D4and the input voltage (Vint) of pulse width modulator (PWM) 132. Theanode of diode D4 may couple to the cathode of diode D3 and a first endof capacitor C5. The second end of capacitor C5 may couple to a firstend of inductor L6 and provide return connection RET6. The second end ofinductor L6 may couple to the anode of diode D3. Both PWM 132 and chargepump 130 provide respective return paths RET5 and RET6. Return pathsRET4, RET5 and RET6 may be coupled together. Inductors L4, L5 and L6 maybe all mutually coupled together on the same core CR1, and the output ofcircuit 111 a on inductor L4 may be coupled back to the input ofcoupling circuit 120 on inductor L5. Charge pump 130 may be realized bya Switched-Capacitor Voltage Converter MAX1680C/D® (Maxim IntegratedProducts, 120 San Gabriel Drive, Sunnyvale, Calif. USA), which maydouble input voltage (Vin1) on output Vout1. PWM 132 may be realized byuse of the LTC®6992 a silicon circuit with an analog voltage-controlledpulse width modulation (PWM) capability by Linear Technology Corporation1630 McCarthy Blvd., Milpitas, Calif., USA.

Reference is now again made to FIG. 1Q and again to FIG. 1H, which showsa flowchart of method 1000, according to illustrative embodiments.Switch BP1 may couple (step 1003) across the outputs of power modules103 where there may be a series string of power module 103 outputs. Atdecision step 1005, if a power module 103 does not work, switch BP1draws the current in the series string (Istring) in a path around fromthe output of an inactive power module 103 (step 1007).

At decision step 1005, a first bypass current conduction of diode PD1may be an indication of power module 103 and/or power source 101 notfunctioning correctly. Methods described below and decision steps inparticular assume that so called ‘decisions’ are made by virtue of aconfiguration of the analog circuits used below to implement couplingcircuit 120, switch BP1 and circuit 111 a in bypass circuit 115 c. Assuch, steps in method 1000 and indeed in steps of the other methodsdescribed below might not preclude the use of digital methodologies suchas use of a microprocessor or microcontroller and associated algorithmto sense and control the operation of a bypass switch which may includecoupling to circuit 120, switch BP1 and circuit 111 a in bypass circuit115. Steps in method 1000 and indeed in steps of the other methodsdescribed below might not preclude the use of any number ofimplementations that combines both analog and digital methodologies.

As with analog circuits, the configuration may include calculation andselection of component values, types of components and theinterconnections of components as part of the circuit design of couplingcircuit 120, switch BP1 and circuit 111 a in bypass circuit 115 c. Theconfiguration may be based therefore, on the normal operating parametersor non-normal operating parameters of power systems 100 a/100 describedabove and in power systems described below. As such, the configurationwith respect to the decision aspect of the decision steps describedbelow may be responsive analog circuit wise to an event such as thebreakdown or failure of a power module 103 and/or power source 101, soas to provide a bypass of the power module 103 and/or power source 101.

The configuration may also give the decision aspect of the decisionsteps described below so as to be responsive to an event such as a powermodule 103 and/or power source 101 reverting back to normal operation soas to remove a bypass of a power module 103 and/or power source 101. Theindication according to the configuration may cause the subsequentactivation of switch BP1 (step 1007) to be ON, so that the output of amalfunctioning power module 103 is bypassed. Otherwise, switch BP1remains OFF so that the bypass function of switch BP1 is inactive (step1003).

The attempt at pushing current flow of current through a non-functioningpower module 103 may be caused by an increase in voltage output of theother power modules 103, which may cause diode PD1 to become forwardbiased. Whereas when a normal operation of power module 103 exists,diode PD1 and the MOSFET of switch BP1 are reversed biased (the MOSFETis OFF). The forward biasing of diode PD1 may cause current Istring toflow from anode to cathode of diode PD1 in a first bypass currentconduction of diode PD1. The forward biasing of diode PD1, similarlycause the forward biasing of switch Q4. The first bypass currentconduction of diode PD1 and the forward voltage of diode PD1 may beapplied to the input of circuit 111 a, which may cause the oscillationof circuit 111 a. The output oscillations of circuit 111 a may be fedback to the input of switch BP1 via coupling circuit 120. The output ofcoupling circuit 120 connects to the gate of the MOSFET of switch BP1.The output of coupling circuit 120 applied to the gate of the MOSFET ofswitch BP1 may be sufficient to cause the MOSFET of switch BP1 to switchON, so that switch BP1 is activated at step 1007. In step 1007, circuit111 a initiates the continuous operation of switch BP1 as soon as thediode PD1 conducts, and later by use of switch Q4 to maintain thecontinuous operation of switch BP1 such that the voltage (Vds) betweendrain (d) and source (s) of switch BP1 remains low at substantially upto 100 milli-volts (mv).

At decision step 1009, if inactive power module 103 remains inactive,then the MOSFET of switch BP1 remains ON so that switch BP1 remainsactivated at step 1007. However, when power module 103 starts to becomeactive, both the MOSFET and diode PD1 of switch BP1 and switch Q4 becomereverse biased. Power module 103 may become active because a panelcoupled to power module may become un-shaded for example. The reversebias voltages of both the MOSFET and diode PD1 of switch BP1 and switchQ4 applied to the input of circuit 111 a at terminals A and B may causethe ceasing of the oscillations of circuit 111 a. The outputoscillations of circuit 111 a ceasing fed back to the input of switchBP1 via coupling circuit 120 may be sufficient to cause the MOSFET ofswitch BP1 to switch OFF so that switch BP1 is de-activated at step1011. The reduction of voltage applied to the gate of the MOSFET causesthe MOSFET to turn OFF. Alternatively, sensors 125 under control ofcontroller 105 or some other controller may sense the reverse biasvoltages of both the MOSFET and diode PD1 of switch BP1. As a result ofthe reverse biases being sensed, switch BP1 may be switched OFF andpower from driver circuitry such as driver circuitry 170 for example,may be allowed to be resupplied to the switches of power module 103 toallow power module 103 to function as normal. With the power modules 103functioning normally switch BP1 is now inactive (OFF) but still coupledat terminals A and B (step 1003).

Operation of Circuit 111 a

Reference is now made again to FIG. 1Q and FIG. 1R, which showrespectively bypass 115 c and a flow chart showing further details ofstep 1007, according to illustrative embodiments. Step 1007 occurs if apower module 103 does not work, so that switch BP1 draws the current inthe series string (Istring) in a path around the output of an inactivepower module 103 in a series string of power module 103 outputs. Inoperation of circuit 111 a, a switch and its diode may be incorporatedinto charge pump 130 or may be attached thereto. The switch (not shownbut similar in function to switch Q3 and diode BD2 in FIG. 1I) may blockleakage current through bypass switch BP1 and block reverse voltageacross bypass switch BP1. The blocking of reverse voltage may be whenthe voltage at terminal A may be much greater than the voltage atterminal B such a situation may be when the power module 103 isoperating correctly at step 1003. The switch and its operation may beignored for ease of the following discussion and is considered to be ON.

In decision step 1303, the continuous operation of switch BP1 in bypassof a power module 103 output begins as soon as the diode PD1 of switchBP1 conducts in a first bypass current conduction. After the firstbypass current conduction, a first stage of the continuous operation ofswitch BP1 may be established primarily by use of charge pump 130, PWM132 and switch Q4. After several possible cycles as described in thesteps which follow by use of charge pump 130, PWM 132 and switch Q4, thevoltage produced by inductor L6 may be greater than the output voltageVout1 of charge pump 130 which initiates a second stage of thecontinuous operation of switch BP1. The time constant to chargecapacitor C5 may be smaller than the time constant to charge capacitorC4. The difference in time constants between capacitors C5 and C4 mayfacilitate the use of charge pump 130 and switch Q4 to operate switchBP1 in the first stage until the second stage. In the second stage, theoperation may be mainly with the continuous operation of PWM 132, switchQ4 and when the voltage produced by inductor L6 may be greater than theoutput voltage Vout1 of charge pump 130.

In decision step 1303, diode PD1 makes a first bypass current conductionof inductor L4 in step 1305 which induces voltages across inductors L5and L6 while bypass switch BP1 may be positively biased with respect tooutput voltage (VAB) of power module 103. Bypass switch BP1 beingpositively biased with respect to output voltage (VAB) of power module103 may signify that power module 103 may be not functioning and needsto have its output bypassed. The induced voltage VL5 of inductor L5 isrectified by diode D2 to charge capacitor C4. The voltage of chargedcapacitor C4 is applied to the gate (g) of bypass switch BP1, so thatbypass switch BP1 is ON for the first bypass current conduction and forboth the first and second stages described in further detail below.

The first bypass current conduction of inductor L4 that may be throughdiode PD1 may be when a low amount of power may be being produced bypower sources 101 and respective power modules 103. An example of thelow amount of power may be when power sources 101 may be photovoltaicpanels that have just begun to be illuminated at dawn for example, orwhen a photovoltaic panel may be substantially shaded. If enough powermay be produced by power sources 101 at decision step 1303, circuit 111a continues to oscillate with the substantial use of charge pump 130 forseveral possible cycles until enough power may be produced by powersources 101.

The principal of operation, for either the first bypass currentconduction or for the first stage may be that inductor L4 with currentflowing through inductor L4 from the first bypass current conductionand/or followed by the use of switch Q4 may be mutually coupled toinductors L5 and L6 via inductor L4. Current flowing through L4 causescurrent to flow in inductors L5 and L6 (step 1309) and the applicationof PWM 132 voltage Vout2 to the gate (g) of switch Q4 (step 1311). Theapplication of PWM 132 voltage Vout2 to the gate (g) of switch Q4 may beby virtue of the output voltage Vout1 of charge pump 130 applied to theinput (Vin2) of PWM 132. The output voltage Vout1 of charge pump 130applied to the input (Vin2) of PWM 132 further causes switch Q4 to startto conduct current between source (s) and second terminals of switch Q4so that Q4 is ON for a time period ton. Discharge of inductor L4 (step1313) continues in decision step 1315 until the end of time period ton.At end of time period ton the application of PWM 132 voltage Vout2 tothe gate (g) of switch Q4 turns Q4 OFF for a time period toff.

Inductors L4, L5 and L6 may be all mutually coupled together on the samecore CR1, as such, the output of circuit 111 a on inductors L5 and L6may be coupled back to the input of coupling circuit 120 to inductor L5.The mutual coupling between inductor L4 and inductors L5 and L6 may besuch that inductors L5 and L6 have a greater number of turns thaninductor L4 so that the voltages induced into inductors L5 and L6 may bemuch greater by virtue of the well-known transformer equations:

$\frac{VL4}{VL5} = {\frac{NL4}{NL5}\mspace{14mu}{and}}$$\frac{VL4}{VL6} = \frac{NL4}{NL6}$

Where VL4, VL5 and VL6 are the respective voltages of inductors L4, L5and L6. NL4, NL5 and NL6 are the respective number of turns of inductorsL4, L5 and L6. The greater voltages induced into inductors L5 and L6 mayallow for operation of switch BP1, switch Q4, charge pump 130 and PWM132. Whereas without the greater voltages induced, switch BP1, switchQ4, charge pump 130 and PWM 132 might not be able to operate otherwise.

Until after several possible cycles as described in the steps 1309-1317above, the voltage produced by inductor L6 and rectified by diode D3 maybuild up to be greater than the output voltage Vout1 of charge pump 130rectified by diode D5. When the voltage produced by inductor L6 andrectified by diode D3 may be greater than the output voltage Vout1 ofcharge pump 130 rectified by diode D5, a second stage begins. The secondstage of the continuous operation of switch BP1 begins by theapplication of voltage rectified by diode D3 applied to the input (Vint)of PWM 132. The second stage of the continuous operation of switch BP1continues the same way as described previously in steps 1309-1317, butwith substantial use of PWM 132 and switch Q4.

Inherent stabilization of bypass circuit 115 c may be established byvirtue of the feedback loop established from the output of circuit 111 aback to the input of circuit 111 a via the rectified outputs ofinductors L5 and L6 (across capacitors C4 and C5) responsive to theoutput of power modules 103 and/or power sources 101. The feedback loopresponsive to the output of power modules 103 and/or power sources 101establishes and maintains the activation of switch BP1 to be ONcontinuously at step 1007 until a power module 103 and/or power source103 becomes inactive. Switch BP1 at step 1007 may be forward biased withrespect to terminals A and B during bypass mode and the gate (g) ofswitch BP1 may have voltage applied which may be such that switch BP1may be continuously ON for the time period that the non-functioningpower module 103 is to be bypassed.

Likewise, the feedback loop responsive to the output of power modules103 and/or power sources 101 establishes and maintains the deactivationof switch BP1 to be OFF continuously at step 1011 until a power module103 and/or power source 103 becomes once again inactive. Switch BP1 maybe reverse biased with respect to terminals A and B during bypass modeand voltage applied to the gate (g) of switch BP1 may be such thatswitch BP1 is continuously OFF for the time period that the functioningpower module 103 is required not to be bypassed at step 1011. Inherentstabilization may occur when switch BP1 may be ON at step 1007, so thatas the drain to source voltage Vds falls, the gate (g) to source (s)voltage Vgs also falls. Similarly, stabilization of bypass circuit 115 cmay be established when switch BP1 may be OFF at step 1011, so that asthe drain (d) to source (s) voltage Vds rises, the gate (g) to source(s) voltage Vgs also rises.

Reference is now made to FIG. 1S, which shows a power system 100 c,according to illustrative embodiments. Connection configuration 104 ashows power source 101 with direct current (DC) output terminals coupledto input terminals of power module 103 at terminals C and D. Powermodule 103 has a bypass circuit 115 coupled to the output terminals ofpower module 103 at terminals A and B.

Connection configuration 104 c shows multiple power sources 101 outputscoupled to respective bypass circuits 115 at terminals A and B. Themultiple power sources 101 outputs may be coupled in a series connectionwith direct current (DC) output terminals of the series connectioncoupled to the input terminals of power module 103 at terminals C and D.A bypass circuit 115 may be coupled to the output terminals of powermodule 103 at terminals A and B.

The outputs of power modules 103 may be coupled in series to form aseries coupled string of power module 103 outputs. The series coupledstring of power module 103 outputs, with a voltage output Vstring may becoupled across the input of system power device 139. System power device139 may be a direct current (DC) to DC converter or may be DC toalternating current (AC) inverter supplying power to load 107.

Assuming power sources 101 may be photovoltaic (PV) panels, if a panelis shaded with shade 155, as shown in connection configuration 104 c,the current (Isource) passing through the shaded panel may be offered analternative, parallel path around the inactive panel, and the integrityof the shaded panel may be preserved. The purpose of bypass circuits 115coupled across the outputs of panels/power sources 101 may be to be thealternative, parallel path to draw the current away from a shaded panelassociated with its respective bypass circuit 115. Bypass circuits 115become forward biased when their associated shadowed panel becomesreverse biased. Since the panels and the associated bypass circuits 115may be in parallel, rather than forcing current through the shadowedpanels, the bypass circuits 115 draw the current away from the shadowedpanels and completes the electrical current to maintain the connectionto the next panel in a string of series coupled power sources as shownin connection configuration 104 c. Use of bypass circuits 115 withrespect to multiple panels wired in series allows for power to be usedfrom the remaining non-shaded panels whereas placing the bypass circuiton just the output of power module 103 only in connection configuration104 c may prevent utilization of the power produced by the remainingnon-shaded panels.

Similarly, if a power module 103 becomes inactive, the current (Istring)passing through the inactive power module 103 may be offered analternative, parallel path around the outputs of the inactive powermodule 103. The purpose of bypass circuits 115 coupled across theoutputs of power modules 103 may be to draw the current away from theoutput of an inactive power module 103 associated with its respectivebypass circuit 115. Bypass circuits 115 become forward biased when theirassociated inactive power module 103 become reverse biased. Since theoutput of power module 103 and the associated bypass circuits 115 may bein parallel, rather than forcing current through an inactive powermodule 103, the bypass circuits 115 draw the current away from theoutput of an inactive power module 103 and completes the electricalcurrent Istring to maintain the connection for current Istring to thenext power module 103 output in a string of series coupled power moduleoutputs 103 as shown.

It is noted that various connections are set forth between elementsherein. These connections are described in general and, unless specifiedotherwise, may be direct or indirect; this specification is not intendedto be limiting in this respect. Further, although elements herein aredescribed in terms of either hardware or software, they may beimplemented in either hardware and/or software. Further, elements of oneembodiment may be combined with elements from other embodiments inappropriate combinations or sub-combinations. Examples above haveutilized analog circuits for implementation of coupling circuits 120 andcircuits 111/111 a used to respectively activate or deactivate a bypassof a non-functioning and functioning power module 103 and/or powersource output in a series string of power module 103 and/or power sourceoutputs. Alternatively, the non-functioning power module 103 may utilizeauxiliary power circuit 162 and sensors 125 to sense a non-functioningpower module 103 output so as to bypass the output of thenon-functioning power module 103 output by turning switch BP1 ON (step1007). Similarly, sensors 125 may be utilized to sense a functioningpower module 103 output so as to not bypass the output of thefunctioning power module 103 output by turning switch BP1 OFF (step1011).

Reference is now made to FIG. 1T, which shows a photovoltaic (PV) systemaccording to illustrative embodiments. Power system 100T may havemultiple PV strings 103T coupled in parallel between power buses 120Tand 130T. Each of the PV strings 103 may have multiple power sources 101and multiple power devices 200. Power sources 101 may include one ormore photovoltaic cell(s), module(s), panel(s) or/or photovoltaicshingle(s). Photovoltaic shingles, are solar panels designed to looklike and function as conventional roofing materials, such as asphaltshingle or slate, while also producing electricity. Solar shingles are atype of solar energy solution known as building-integrated photovoltaics(BIPV). According to some aspects, power sources 101 shown as PVgenerators may be replaced by other power sources, for example, directcurrent (DC) batteries or other DC or alternating current (AC) powersources. Each power device 200 may include a control device and acommunication device, and may be operated to disconnect a PV generatorconnected at the power device inputs when receiving (e.g., via thecommunication device) a command to disconnect PV generators. Powersystem 100T may include power buses 120T and 130T, which may be input tosystem power device 110T.

According to some aspects, system power device 110T may include a DC/ACinverter (e.g., when the input power is DC power), an AC/AC converter(e.g., when the input power is AC power), and may output AC power to apower grid, to a home, or to other destinations. According to someaspects, system power device 110T may include or be coupled to a controldevice and/or communication device for controlling or communicating withpower devices 200. For example, system power device 110 may have acontrol device such as a microprocessor, digital signal processor (DSP),application specific integrated circuit (ASIC) and/or a fieldprogrammable gate array (FPGA) configured to control the operation ofsystem power device 110T.

System power device 110T may further include a communication device(e.g., a power line communication circuit, an acoustic communicationsdevice and/or a wireless transceiver) configured to communicate withlinked communication devices included in power devices 200 and transmitoperational commands and/or receive reports from communication devicesincluded in power devices 200.

According to some aspects, power buses 120T and 130T may be furthercoupled to energy storage devices such as batteries, supercapacitors,flywheels or other storage devices.

According to some aspects, it may be desirable to bypass (e.g., providea low-impedance current path across) one or more power sources 101and/or power devices 200. For example, in case of a malfunctioning orunder-producing power source (e.g., PV generator) 101 or amalfunctioning PV power device 200, it may be beneficial to bypass themalfunctioning or under-producing PV module to enable continued powerproduction from power system 100T.

Safety regulations may define a maximum allowable voltage between powerbuses 120T and 130T and any other point in power system 100T, duringboth regular operating conditions and during potentially unsafeconditions. Safety regulations may also define a maximum allowablevoltage between any two voltage points in power system 100T. In somescenarios, in may be beneficial to bypass (e.g., by short-circuitingand/or disconnecting) one or more of power sources 101 in a PV string103T in response to an unsafe condition in power system 100T.

Reference is now made to FIG. 2 , which illustrates circuitry that maybe included in a power device such as power device 200, according toaspects of the disclosure herein. Power device 200 may include powerconverter 201. Power converter 201 may include a DC/DC converter such asa Buck, Boost, Buck/Boost, Buck+Boost, Cuk, Flyback, charge pump and/orforward converter. According to some aspects, power converter 201 mayinclude a DC/AC converter (also known as an inverter), such as amicro-inverter. Power converter 201 may have two input terminals and twooutput terminals, which may be the same as the input terminals andoutput terminals of power device 200. According to some aspects, powerdevice 200 may include an MPPT circuit 205, configured to extractincreased power from a power source coupled to power device 200.According to some aspects, power converter 201 may include MPPTfunctionality. According to some aspects, MPPT circuit 205 may implementimpedance matching algorithms to extract increased power from a powersource coupled (e.g., directly connected) to the input of power device200.

Power device 200 may further include a controller 204 such as an analogcontrol circuit, a microprocessor, Digital Signal Processor (DSP),Application-Specific Integrated Circuit (ASIC), and/or a FieldProgrammable Gate Array (FPGA). Controller 204 may control and/orcommunicate with other elements of power device 200 over common bus 290.According to some aspects, power device 200 may include circuitry and/orsensor(s)/sensor interface(s) 203 configured to measure parametersdirectly or receive measured parameters from connected sensor(s)/sensorinterface(s) 203 configured to measure parameters on or near the powersource, such as the voltage and/or current and/or power output by thepower source. According to some aspects, sensor(s)/sensor(s) interfaces203 may be configured to sense parameters on the output of power device200. According to some aspects, the power source may be a PV generatorincluding PV cells, and sensor(s)/sensor interface(s) 203 may directlymeasure or receive measurements of the irradiance received by the PVcells, and/or the temperature on or near the PV generator.

According to some aspects, power device 200 may include communicationdevice 202, configured to transmit and/or receive data and/or commandsfrom other devices such as system power device 110T of FIG. 1T.Communication device 202 may communicate using power line communication(PLC) technology, acoustic communications, or wireless communicationtechnologies such as ZIGBEE™, BLUETOOTH™, Wi-Fi, cellular communicationor other wireless methods. According to some aspects, power device 200may include a memory device 208, for logging measurements taken bysensor(s)/sensor interface(s) 203 to store code, operational protocolsor other operating information. Memory device 208 may be flash,electrically erasable programmable read-only memory (EEPROM), randomaccess memory (RAM), solid state devices (SSD) or other types ofappropriate memory devices.

Power device 200 may have safety devices 206 (e.g., fuses, circuitbreakers and/or Residual Current Detectors). Safety devices 206 may bepassive or active. For example, safety devices 206 may include one ormore passive fuses disposed within power device 200 and designed to meltwhen certain current flows through it, disconnecting part of powerdevice 200 to avoid damage. According to some aspects, safety devices206 may have active disconnect switches, configured to receive commandsfrom a controller (e.g., controller 204) to disconnect portions of powerdevice 200, or configured to disconnect portions of power device 200 inresponse to a measurement measured by a sensor (e.g., sensor(s)/sensorinterface(s) 203). According to some aspects, power device 200 may havean auxiliary power circuit 207, configured to output power suitable foroperating other circuitry components (e.g., controller 204,communication device 202). Communication, electrical coupling and/ordata-sharing between various components of power device 200 may becarried out over common bus 290.

Power device 200 may have a bypass circuit 209 (also referred to hereinas “safety module”) coupled between the inputs and/or outputs of powerconverter 201. According to some aspects, bypass circuit 209 may becoupled to the inputs a and b of power device 200. According to someaspects, bypass circuit 209 may be coupled to the outputs c and d ofpower device 200. In the illustrative power device 200 shown in FIG. 2 ,a first bypass circuit 209 may be connected between the inputs a and bto power device 200 (e.g. bypass circuit 209 a as shown in FIG. 2A), anda second bypass circuit 209 (e.g., bypass circuit 209 b as shown in FIG.2B) may be connected between the outputs c and d of power device 200.Bypass circuit 209 may be controlled by controller 204. If an unsafecondition, malfunction and/or underperformance condition is detected,according to some aspects, controller 204 may enable bypass circuit 209,bypassing the inputs a and b to power device 200. Bypass circuit 209 maybypass the inputs a and b to power device 200 by short circuiting theoutputs c and d and/or short circuiting the inputs a and b. According tosome aspects, bypass circuit 209 may disconnect an input, a or b ofpower device 200 from the outputs c and d of power device 200 and shortcircuit the outputs c and d of power device 200.

According to some aspects, bypass circuit 209 may be integrated in powerconverter 201. For example, power converter 201 may have multipleswitches (e.g., metal-oxide-semiconductor field-effect transistors(MOSFETs) such as shown in FIG. 2B) that may be used for powerconversion under safe conditions, and may short circuit either theinputs or outputs of power converter 201 under unsafe conditions such asa malfunction condition or an underproduction condition. According tosome aspects, bypass circuit 209 may provide bidirectional bypassfunctionality, while also allowing a regulated voltage for controllingswitches of power converter 201.

Reference is made to FIG. 2A, which illustrates circuitry that may beincluded in bypass circuit 209 a. FIG. 2 illustrates two bypasses 209 aspart of power device 200, and in series with power converter 201.According to some aspects, a bypass circuit 209 a may be in parallel tothe power device. Bypass circuit 209 a may have a first input A and asecond input B, where inputs A and B may be connected to a power string,for example, as part of PV string 103 of FIG. 1T. Bypass circuit 209 amay include a diode bridge 250 including diodes DB1-DB4. A switch (e.g.,MOSFET) QB1 may be connected between the output nodes C and D of thediode bridge 250 in bypass circuit 209 a. According to some aspects,power systems supported by embodiments herein, a string currentI_(string) may be in DC form. For example, bypass circuit 209 a may becoupled to a power converter connected to a battery, where the batterymay be charged (resulting in current flow from node A to node B) anddischarged (resulting in current flow from node B to node A). WhenI_(string) is flowing from point A to point B, I_(string) may enterbypass circuit 209 a, flow through DB2 and reach switch QB1. When bypasscircuit 209 a is disabled, switch QB1 is OFF, bypass circuit 209 a mayeffectively operate as an open circuit, and the string currentI_(string) may flow through and be processed by a power converter (e.g.,a micro-inverter) coupled in parallel with bypass circuit 209 a (notexplicitly shown in FIG. 2A, but shown in FIG. 3 ). When bypass circuit209 a is enabled, switch QB1 is ON and I_(string) flows through switchQB1 and diode DB4, out of bypass circuit 209 a to point B. In somescenarios (e.g. discharging a battery), I_(string) may flow from point Bto point A. I_(string) may enter bypass circuit 209 a and flow throughdiode DB1 and reach switch QB1. When bypass circuit 209 a is disabled,switch QB1 is OFF and bypass circuit 209 a is an open circuit. Whenbypass circuit 209 a is enabled, switch QB1 is ON and I_(string) mayflow through switch QB1 and diode DB3, out of bypass circuit 209 a topoint A.

According to some aspects, I_(string) may be in an AC form (e.g., whenpower converter 201 is a DC/AC converter), and the I_(string) currentmay flow from A to B during a first part of a cycle and from B to Aduring a second part of the cycle. In each flow direction of I_(string),because of the diode bridge 250 in bypass circuit 209 a, the voltageV_(B+) may be larger than V_(B−) which may prevent any current fromflowing through the passive diode in switch QB1. Because of the diodebridge 250 in bypass circuit 209 a, the voltage on switch QB1 may bepositive (V_(B+)−V_(B−) >0). Because the positive voltage across switchQB1 may always be positive, the voltage drop across switch QB1 may beprovided to a controller (e.g. an analog or digital controller)configured to drive switch QB1 to provide a bypass path, according toillustrative features disclosed below.

Reference is now made to FIG. 2B, which illustrates bypass circuit 209b, where the inputs of bypass circuit 209 b are connected to a string,for example PV string 103 of FIG. 1T. Bypass circuit 209 b may have aMOSFET bridge 260 including MOSFETs QB2-QB5. The outputs of the MOSFETbridge 260 in bypass circuit 209 b may be connected with a switch QB1between them. According to some aspects, I_(string) may be in DC form.In a scenario where I_(string) is flowing from point A to point B,I_(string) may enter bypass circuit 209 b, flow through QB4 (which maybe ON or OFF) and reach switch QB1. When bypass circuit 209 b isdisabled, MOSFET QB1 may be OFF and bypass circuit 209 b may be an opencircuit. When bypass circuit 209 b is enabled, switch QB1 is ON andI_(string) may flow through switch QB1 and MOSFET QB2 (which may be ONor OFF), and may flow through bypass circuit 209 b to point B. In somescenarios, I_(string) may flow from point B to point A. I_(string) mayenter bypass circuit 209 b and flow through switch QB3 (that may be ONor OFF) and reach switch QB1. When bypass circuit 209 b is disabled,switch QB1 may be OFF and bypass circuit 209 b may be an open circuit.When bypass circuit 209 b is enabled, switch QB1 may be ON andI_(string) may flow through switch QB1 and MOSFET QB5 (that may be ON orOFF) through bypass circuit 209 b to point A. According to some aspects,I_(string) may be in an AC form and the I_(string) current may flow fromA to B during a first part of a cycle and from B to A during a secondpart of the cycle. In each direction of I_(string), because of theMOSFET bridge 260 in bypass circuit 209 b, the voltage level V_(B+) maybe larger than voltage level V_(B−) which may prevent substantialcurrent from flowing through the passive diode in MOSFET QB1. Because ofthe MOSFET bridge 260 in bypass circuit 209 b, the voltage on MOSFET QB1may be positive (V_(B+)−V_(B−)>0). Each one of MOSFETs QB2-QB5 may be ONor OFF when bypass circuit 209 b is enabled and/or disabled, where whenMOSFETs QB2-QB5 are OFF current may flow through the passive diodes inMOSFETs QB2-QB5, and when MOSFETs QB2-QB5 are ON the current may flowthrough the MOSFETs themselves. MOSFETs QB1-QB5 may be powered by anexternal auxiliary power circuit such as auxiliary power circuit 207 ofFIG. 2 .

According to some aspects, MOSFETs QB2-QB5 of bypass circuit 209 b maybe part of an inverter (e.g., a microinverter). For example, powerconverter 201 of FIG. 2 may be an inverter. When bypass circuit 209 b isdisabled, switches QB2-QB5 may be switched at an inverter frequency(e.g., 10 kHz, 20 kHz, 100 kHz, 200 kHz or even higher) and switch QB1may be OFF. When bypass circuit 209 b is enabled, switches QB2-QB5 mayswitch at a frequency of a grid-frequency of current flowing throughI_(string) (e.g., 50 Hz or 60 Hz) and switch QB1 may be ON,short-circuiting outputs C and D. According to some aspects, bypasscircuit 209 b may be connected in parallel to a power device, where whenbypass circuit 209 b is disabled switch QB1 is OFF and I_(string) mayflow through the power device parallel to bypass circuit 209 b. Whenswitch QB1 is ON and bypass circuit 209 b is enabled, the outputs ofpower device parallel to bypass circuit 209 b (which may be the same aspoints A and B) may be short-circuited, allowing the current I_(string)to flow through bypass circuit 209 b and bypass the power device.

Reference is now made to FIG. 2C, which shows part of a power device 210according to one or more illustrative aspects of the present disclosure.Power device 210 may include power converter 211, which may be the sameas power converter 201 of FIG. 2 . According to some aspects, powerdevice 212 may have a bypass circuit 212 a configured to bypass theinputs of power device 210. Bypass circuit 212 a may be configured toprovide a bypass path across the outputs of power device 210 and/ordisconnect an input of power device 210 from the outputs of power device210. According to some aspects, power device 210 may have a bypasscircuit 212 b configured to bypass power device 210 and/or powerconverter 211. Bypass circuit 212 b may be configured to provide abypass path by short circuiting the outputs of power device 210.

According to some aspects, bypass circuit 212 b may be coupled to abypass circuit having a bimetallic strip BMS1. Bimetallic strip BMS1 mayinclude two materials with different expansion coefficients bondedtogether. Bimetallic switch BMS1 may operate as a switch, such that whenBMS1 is heated at a first temperature, the first material including BMS1may curve in a first direction and at a second temperature the secondmaterial including BMS1 may curve in a second direction. For example,the first material may curve at a first temperature of 40° C. and thesecond material may curve at a second temperature of 200° C. BMS1 may beconfigured to short circuit the outputs of power device 212 out1 andout2 in response to a state of overheating (for example, when thetemperature surrounding BMS1 is over 200° C.) and to disconnect outputsout1 and out2 when the temperature is beneath 200° C. The coupling ofbypass circuit 212 b with BMS1 may be such that BMS1 is positioned inproximity to a certain element in bypass circuit 212 b (e.g., MOSFET ordiode). The proximity of BMS1 to bypass circuit 212 b may be such thatBMS1 may sense a temperature level similar to the certain element inbypass circuit 212 b. When bypass circuit 212 b is enabled and currentis flowing through bypass circuit 212 b the temperature of certainelements may rise, and in a state of overheating, BMS1 may be configuredto switch ON, creating another path for the current to flow throughother than bypass circuit 212 b, which may lower the temperature at theelement of bypass circuit 212 b. According to some aspects, power device210 may have a bypass circuit 212 a. According to some embodiments,bypass circuit 212 a may be configured to short circuit the outputs ofpower device 210. Parallel to bypass circuit 212 a may be a bimetallicswitch BMS2. BMS2 may be similar to or the same as BMS1, where BMS1 maybe placed between the outputs of power device 210 out1 and out2 and BMS2may be placed between the inputs of power device 210 in1 and in2. BMS2may be positioned in proximity to a certain element in bypass circuit212 a (e.g., MOSFET). The proximity of BMS2 to bypass circuit 212 a maybe such that BMS2 may sense a temperature level similar to the certainelement in bypass circuit 212 a. When bypass circuit 212 a is enabledand current is flowing through bypass circuit 212 a, the temperature ofcertain elements (e.g. a switch QB1) may rise, and in a state ofpossible or potential overheating, BMS2 may be configured to switch ON,creating another path for the current to flow through, which may lowerthe temperature in bypass circuit 212 b. According to some aspects BMS3may be coupled to the certain element in bypass circuit 212 a.

According to some aspects, power device 210 may include bypass circuit212 a. A bimetallic strip BMS3 may be coupled to bypass circuit 212 a.BMS3 may be similar to BMS1, where BMS1 may be placed between theoutputs of power device 210 out1 and out2 and BMS3 may be placed betweenthe low side of the inputs of power device 210, node in3, and powerconverter 211 low side, node in2. According to some aspects, BMS3 may bepositioned in proximity to a certain element of bypass circuit 212 a. Ina scenario where bypass circuit 212 a is enabled, and the inputs topower device 210 are short circuited, the temperature of the certainelement in bypass circuit 212 a may rise. BMS3 may be “normally ON”during normal operating conditions, and configured to create an opencircuit and mechanically disconnect an input of power device 210 fromthe outputs of power device 210 which may lower the current flowingthrough bypass circuit 212 a and specifically the certain element inbypass circuit 212 a, and by lowering the current the temperature on thecertain element may drop. According to some aspects, power device 210may have only a bypass circuit including BMS1. According to someaspects, power device 210 may have a bypass circuit including BMS2.According to some aspects, power device 210 may have a bypass circuitBMS3. According to some aspects, power device 210 may have a bypasscircuit including more than one bimetallic switch, such as BMS2 andBMS3.

Bimetallic switches BMS1 and/or BMS2 and/or BMS3 may be used as aprimary bypass mechanism of power device 210, or as a backup bypassmechanism while the primary backup mechanism may be similar to or thesame as bypass circuit 209 a of FIG. 2A and/or 209 b of FIG. 2B, wherebackup bypass mechanism may be needed in a scenario where the primarybypass circuit fails, overheats, etc.

According to some aspects, one or more of bimetallic switches BMS1-BMS3,may be replaced with an active electronic switch, for example, ametal-oxide-semiconductor field-effect transistor (MOSFET),insulated-gate bipolar transistor (IGBT), Bipolar Junction Transistor(BJT), relay switch etc. According to some aspects, BMS1 and/or BMS2 maybe replaced with a passive switch, for example, a diode.

Reference is made again to FIG. 2 . According to some aspects, powerdevice 200 may have bypass circuit 209 coupled to the outputs of powerdevice 200. Bypass circuit 209 may have a bypass circuit similar to orthe same as bypass circuit 209 a of FIG. 2A and/or bypass circuit 209 bof FIG. 2B. In some embodiment, bypass circuit 209 may have a bimetallicstrip similar to or the same as bimetallic strip BMS1 of FIG. 2C.

Reference is made again to FIG. 2 . According to some aspects, powerdevice 200 may have bypass circuit 209 coupled to the inputs of powerdevice 200. Bypass circuit 209 may have a bypass circuit similar to orthe same as bypass circuit 209 a of FIG. 2A and/or bypass circuit 209 bof FIG. 2B. In some embodiment, bypass circuit 209 may have a bimetallicstrip similar to or the same as bimetallic strip BMS2 of FIG. 2C.

Reference is now made to FIG. 3 , which shows a block diagram of part ofa power device 300, according to aspects of illustrative embodiments.Power device 300 may be the same as or similar to power device 200 ofFIG. 2 , and may include power converter 301, auxiliary power circuit302, bypass circuit 303, controller 304, and sensor(s)/sensorinterface(s) 305, which may be similar to or the same as power converter201, auxiliary power circuit 207, bypass circuit 209, controller 204,and sensor(s)/sensor interface(s) 203, respectively. Controller 304 maybe operatively connected to sensor(s)/sensor interface(s) 305, wherebysensor(s)/sensor interface(s) 305 may be operatively connected, to senseparameters of power device 300. Power converter 301 converts input poweron terminals V_(in+), V_(in−) to an output power on the output ofconverter 301 as string current I_(string). Bypass 303 may be connectedacross the output of converter 301. Power to operate bypass 303 as wellas power converter 301, controller 304 and/or sensor(s)/sensorinterface(s) 305 may be provided by auxiliary power circuit 302.

According to some aspects, controller 304 may receive a value of aparameter measured by sensor(s)/sensor interface(s) 305, for exampletemperature, voltage and/or current. Controller 304 may compare thevalue of the measured parameter with a maximum threshold and determinethe value of the measured parameter as an unsafe value (e.g., atemperature indicative of overheating of the system, such as 200° C.).Controller 304 may enable bypass circuit 303 in response to determiningthat there is a malfunction and/or underproduction condition in powerdevice 300. Bypass circuit 303 may short circuit the outputs of powerconverter 301 and/or outputs of power device 300. According to someaspects, bypass circuit 303 may be powered by auxiliary power circuit302 with an output voltage of V_(g). The output voltage of auxiliarypower circuit 302 may be determined by controller 304, while controller304 may further determine which switches in bypass circuit 303 to turnON and OFF and when to turn ON and OFF. Auxiliary power circuit 302 mayhave an input voltage of V_(AUX)=V_(B+)−V_(B−), where V_(B+) and V_(B−)may be according to the voltage value at the output of bypass circuit303.

According to some aspects (not explicitly shown), power converter 301may include an inverter, which may include a MOSFET bridge (e.g. bridge260 of FIG. 2B). Power converter 301 may serve as a power converterand/or inverter when power device 300 is enabled and providing power toa solar string having current I_(string). When power device is beingbypassed, power converter 301 may serve as the bypass circuit. In anembodiment where power converter 301 serves as a bypass circuit, powerconverter 301 may include a switch positioned between the two outputs ofthe MOSFET bridge (e.g. QB1 of FIG. 2B) in power converter 301. Theswitch positioned between the two outputs of the MOSFET bridge may be ONwhen bypass is enabled and maybe OFF when bypass is disabled.

Reference is now made to FIG. 3A, which shows an illustration of anauxiliary power circuit 302 a, bypass circuit 303 a and controller 304as part of a power device. Auxiliary power circuit 302 a and bypasscircuit 303 a may be the same as or similar to auxiliary power circuit302 and bypass circuit 303 of FIG. 3 . Controller 304 may receive asignal indicating the bypass circuit 303 a should be enabled, orcontroller 304 may independently determine that bypass circuit 303 ashould be enabled. Bypass circuit 303 a may be implemented in a similarway to bypass circuit 209 b, including a bridge 370 of switches (e.g.MOSFETs) QB2-QB5 where the outputs of the bridge 370 (nodes C and D),are coupled to each other via switch (e.g. MOSFET) QB1. A first input toauxiliary power circuit 302 a may electrically couple to a first outputof bypass circuit 303 a (node C) which may be coupled to the sourceterminal of switch QB1. A second input to auxiliary power circuit 302 amay electrically couple to a second output of bypass circuit 303 a (nodeD) which may be coupled to the drain terminal of switch QB1. Auxiliarypower circuit 302 a may include a power converter 306. Power converter306 may be an AC/DC converter and/or a DC/DC converter. Power converter306 may be configured to convert power from a lower voltage level e.g.0.01[V] to a higher voltage level (e.g., 5 V, 12 V, 100 V, 220 V, andhigher). The power at the outputs of bypass circuit 303 a may have avoltage value of V_(B+)−V_(B−) that may be the same voltage on theinputs to auxiliary power circuit 302 a. The input power to auxiliarypower circuit 302 a may be converted by power converter 306 and may beoutput by auxiliary power circuit 302 a. Auxiliary power circuit 302 amay be configured to provide power to one or more circuits and/ormechanisms in the power device, such as controller 304 and switchesQB1-QB5 of bypass circuit 303 a. Controller 304 may be configured todetermine how much power to feed each switch of switches QB1-QB5. Forexample, I_(string) may be an AC current with a value of:I_(string)=10[A] at a frequency of: f=40 [Hz] and may flow into a firstinput of bypass circuit 303 a. Bypass circuit 303 a may be disabled,switch QB1 may be OFF, and auxiliary power circuit 302 a may draw powerfrom the outputs of bypass circuit 302 b having a voltage value of, forexample, V=V_(B+)−V_(B−)=0.5[V]. Auxiliary power circuit 302 a may drawcurrent according to the voltage required by switches QB1-QB5 (asdetermined by controller 304). Auxiliary power circuit 302 a may outputa voltage value of V_(g) with regard to a neutral point, ground or otherpoint. According to some aspects, controller 304 may switch switchesQB2-QB5 at a frequency of f=50 [Hz], such that switches QB4 and QB2 areON when QB3 and QB5 are OFF, and switches QB2 and QB4 are OFF when QB3and QB5 are ON. Auxiliary power circuit 302 a may draw current frombypass circuit 303 a with a value of, for example, I_(AUX)=0.01[A]. Thecurrent I_(AUX) may be used to power controller 304 as well as auxiliary302 a and bypass circuit 303 a. According to some aspects, auxiliarypower circuit 302 a may include a controller configured to control theswitching of switches QB1-QB5. In a scenario where controller 304decides to enable bypass circuit 303 a, switches QB2-QB5 may be poweredand switched at the same rate as when bypass circuit 303 a is disabled.The voltage value of V=V_(B+)−V_(B−) may change because QB1 may beturned ON, creating a voltage drop depending on characteristics (e.g.,the drain-to-source resistance) of switch QB1, for example,V=V_(B+)−V_(B−)=0.1V. Power converter 306 in auxiliary power circuit 302a may be configured to convert input ultra-low voltages such as 0.1V oreven lower. When controller 304 enables bypass circuit 303 a andcommands auxiliary power circuit 302 a to turn switch QB1 ON, I_(AUX)may grow accordingly to I_(AUX)=0.05 A, to supply enough power to turnswitch QB1 ON.

Reference is now made to FIG. 3B, which shows part of power device 300 baccording to illustrative embodiments. Power device 300 b may includepower converter 301 b, auxiliary power circuit 302 b and controller 304b which may be the same as or similar to power converter 201, auxiliarypower circuit 207 and controller 204 of FIG. 2 . According to someaspects, power device 300 b may be coupled to power source 310. Powersource 310 may be a source which at times provides power and at timesreceives power, for example a battery. According to some aspects,I_(string) may be in DC form during each period of time. When powersource 310 is providing power, the current I_(string) may flow from A toB and when power source 310 is receiving power, I_(string) may flow fromB to A. In an embodiment where I_(string) is in DC form, power converter301 b may be a DC/DC converter. Power device 300 b may have a bypasscircuit 303 b configured to bypass power converter 301 b and/or powersource 310. Bypass circuit 303 b may be a component of power device 300b or power converter 301 b or an independent device configured to coupleto the outputs of power device 300 b or power converter 301 b.

Reference is now made to FIG. 3C, which shows a bypass circuit accordingto illustrative embodiments. Bypass circuit 303 b of FIG. 3B may beimplemented similarly to bypass circuit 303 c of FIG. 3C, having a firstswitch SB1 and a second switch SB2 connected in series. Switches SB1 andSB2 may be coupled to outputs A and B, and nodes C and D may be coupledto the outputs of power converter 301 b. Bypass circuit 303 b may beconfigured to turn switches SB1 and SB2 ON when bypass circuit 303 b isenabled, and turn switches SB1 and SB2 OFF when bypass 303 b isdisabled. Bypass circuit 303 b may receive power from auxiliary powercircuit 302 b. Controller 304 b may be configured to decide to enablebypass circuit 303 b and/or disable bypass circuit 303 b. When bypasscircuit 303 b is disabled and power device 300 b is transferring powerfrom power source 310 to the outputs A and B of power device 300 b ortransferring power from outputs A and B of power device 300 b to powersource 310, the voltage drop across bypass circuit 303 b may be the sameas or similar to the voltage between points A and B, for example, 40[V].Auxiliary power circuit 302 b may have the same or a similar voltage asbypass circuit 302 b, and may transfer power to components in powerdevice 300 b, such as controller 304 b. When bypass circuit 303 b isenabled, outputs A and B are short circuited using switches SB1 and SB2.The voltage between points A and B may drop to 1[V]. The voltage acrossauxiliary power circuit 302 b may drop accordingly. Auxiliary powercircuit 302 b may be configured to transfer power under low voltages tobypass circuit 303 b.

According to some aspects, I_(string) may be in AC form. Bypass circuit303 b may be implemented in a manner the same as or similar to bypasscircuit 303 a. Power converter 301 b may be a DC/AC inverter. Whenbypass circuit 303 b is disabled, switch QB1 (of FIG. 3A) may be OFF andpower converter 301 b may receive I_(string) from outputs of powerdevice 300 b, A and B. Switches QB4 and QB2 may be ON, powered byauxiliary power circuit 302 b. When bypass circuit 303 b is enabled,switch QB1 may turned ON by controller 304 b and auxiliary power circuit302 b.

Reference is now made to FIG. 4 , which illustrates part of a powerdevice 400 according to illustrative embodiments. Power device 400 mayinclude power converter 401, auxiliary power circuit 402, bypass circuit403, and controller 404 that may be the same as or similar to powerconverter 201, auxiliary power circuit 207, bypass circuit 209, nodes a,b, c, d and controller 204 of FIG. 2 , respectively. Bypass circuit 403may be coupled to the outputs of power device 400 and/or the outputs ofpower converter 401 and may be configured to bypass power converter 401.

According to some aspects, auxiliary power circuit 402 may receive powerfrom the inputs to power device 400, a and b, with a voltage value of:V_(in)=V_(in+)−V_(in−). Power may be transferred from a power generator(e.g., power generator 101 of FIG. 1 ) to the inputs a and b of powerdevice 400, at a voltage value of V_(in), and the power may flow from apower generator such as power generator 101 of FIG. 1A. Auxiliary powercircuit 402 may be electrically coupled to the outputs of bypass circuit403, and may receive power from bypass circuit 403 with at voltage valueof V_(B)=V_(B+)−V_(B−). According to some aspects, auxiliary powercircuit 402 may extract power from the inputs to power device 400, A andB, rather than from the outputs of bypass circuit 403 that receivespower from the outputs of power device 400, c and d, for example, if thecurrent I_(string) is in AC form while auxiliary power circuit requirescurrent and voltage in DC form. According to some aspects, auxiliarypower circuit 402 may receive power from the inputs to power device 400,controller 404 may disable bypass circuit 403, for example, bypasscircuit 403 may comprise multiple MOSFETs (i.e., as shown in bypasscircuit 209 b of FIG. 2A), and controller 404 may keep the MOSFETs OFFand not switch them ON and OFF.

In some scenarios, auxiliary power circuit 402 might not be able toreceive power from the inputs to power device 400, for example, if thepower generator configured to output power to power device 400 throughthe inputs of power device 400 is disconnected from power device 400. Insuch a scenario (e.g., where power from the inputs to power device 400is not available), auxiliary power circuit 402 may be powered by powerfrom the outputs of bypass circuit 403. According to some aspects,auxiliary power circuit 402 may have a logic block (e.g., circuit 410shown in FIG. 4A) configured to extract power from the inputs of powerdevice 400 or from bypass circuit 403.

Reference is now made to FIG. 4A, which illustrates a circuit 410configured to disable and enable a bypass circuit. Circuit 410 may bepart of a power device, such as power device 400. The bypass circuit maybe enabled when a switch QB1 is ON and disabled when switch QB1 is OFF.Switch QB1 may be the same as or similar to switch QB1 of FIG. 3A.Switch QB1 may be a MOSFET disposed between points DD and GG. Switch QB1may be configured to bypass a power source 411 and/or a power deviceincluding circuit 410. Power source 411 may have a first output AA and asecond output point GG. Point GG may be used as a reference point incircuit 410 and may be referenced to as a relative ground. Circuit 410may have a resistor R11 disposed between output AA and a point BB. PointBB may be an input to an amplifier Amp1. Amplifier Amp1 may have anegative input and a positive input. Point BB may be at the negativeinput to amplifier Amp1. The positive input to amplifier Amp1 may bepoint H. Between points HH and GG may be a diode D13 configured to allowcurrent to flow from GG to H and to apply a set voltage (e.g., 0.3V,0.5V, 0.7V, 1V) difference between GG and H, setting a reference voltageon the positive input to amplifier Amp1. Resistor R12 may be disposedbetween points BB and GG. Resistors R11 and R12 may be configured tofunction as voltage divider in relation to the voltage of power source411, V_(A)-V_(G). Amplifier Amp1 may have a first output at point EE.Switch QB1 may have a drain terminal connected to point DD, a sourceterminal connected to point GG and a gate terminal connected to pointFF. Resistor R13 may be disposed between points EE and FF and resistorR14 may be disposed between points FF and GG. V_(g) may be the voltageat point FF, where it may be defined by the output voltage fromamplifier Amp1. V_(g) may be the voltage at the gate to switch QB1.Point CC may be the positive power supply on amplifier Amp1 and point GGmay be the negative power supply on amplifier Amp1. Resistor R15 may bedisposed between points HH and DD. Between point CC and DD may be adiode D12 configured to set a voltage difference between point CC andpoint DD. A second diode D11 may be disposed between points AA and CC.

Amplifier Amp1 may be connected between terminals CC and GG forreceiving operational power from power source 411 via diode D11 or fromthe voltage across switch QB1, via diode D12. According to theillustration of FIG. 4A, if the voltage across power source 411 ishigher than the voltage across switch QB1, the operational power foramplifier Amp1 will be drawn from power source 411, and if the voltageacross power source 411 is lower than the voltage across switch QB1, theoperational power for amplifier Amp1 will be drawn from across switchQB1. This may provide the advantage of enabling power supply from powersource 411 if power source 411 is available (which may increaseefficiency), and enabling power supply from across switch QB1 if powersource 411 is unavailable (e.g., if power source 411 is a disconnectedor malfunctioning power source, or a shaded photovoltaic generator).

Optionally, diodes D12 and D11 may be removed, and terminal CC may bedirectly connected to terminal DD (enabling drawing operational power toamplifier Amp1 from across switch QB1) or to terminal AA (enablingdrawing operational power to amplifier Amp1 from power source 411).

Reference is now made to FIG. 4B, which shows a method 420 for enablingbypass according to illustrative embodiments. Method 420 may beimplemented by one or more circuits, analog and/or digital, for examplecircuit 410 of FIG. 4A. Step 420 may include providing power to anamplifier and/or an operational amplifier (e.g., Amp1 of FIG. 4A). Theoperational amplifier may have a positive power supply, and a negativepower supply. According to some aspects, the positive power supply maybe equal to the absolute value of the negative power supply. Accordingto some aspects, the positive power supply may be different than theabsolute value of the negative power supply, for example, the positivepower supply may be 1[V] compared to a relative ground and the negativepower supply may be 0[V] compared to the relative ground. The negativepower supply may be connected to the negative end of a power source. Thenegative end of the power source may be related to as a relative ground.The positive power supply may draw power from a node common to a firstdiode and a second diode. The first diode (e.g. D11 of FIG. 4A) may beconnected to the output of the power source, and the second diode (e.g.D11 of FIG. 4A) may be connected to the positive side of a switchconfigured to enable bypass when ON and disable bypass when OFF (e.g.QB1 of FIG. 4A). The switch may be a MOSFET where the drain may be apositive side of the switch, and the source of the switch may be thenegative side of the switch. The positive power supply of the amplifiermay get the voltage value of the higher voltage between the power sourceand the positive side of the switch.

Step 422 of method 420 may include inputting a first voltage into thenegative input of the operational amplifier and a second voltage to thepositive input of the operational amplifier. The positive voltage may berelated to as a reference voltage. The reference voltage may beconnected to the relative ground with a diode (e.g. D13 of FIG. 4A). Thediode may be configured to maintain a set voltage relative to theground. The positive input to the amplifier may be connected to thepositive end of the power source through a voltage divider (e.g. R11 andR12 of FIG. 4A), to maintain a voltage level appropriate to the voltagelevels that the operational amplifier may receive. The operationalamplifier may be configured to compare the voltage level received fromthe positive end of the power source with the reference voltage. Thevoltage level need for the negative input to be greater than thereference positive input may be determined by the voltage dividerconnecting the positive end of the power source with the negative inputto the amplifier, and the diode connecting the relative ground and thepositive input. In a scenario where the negative input is greater thanthe positive input, the operational amplifier may output a voltage valuesimilar to the relative ground. The output of the amplifier may beconnected to the relative ground with two resistors in series (e.g. R13and R14 of FIG. 4A). The switch configured to enable bypass may have agate connected to a point between the two resistors in series, where thetwo resistors may be configured to be a voltage divider. In such ascenario, where the output voltage of the amplifier is the similar tothe relative ground, the voltage difference between the output of theamplifier, the voltage in between the two resistors and the relativeground may be substantially zero with regard to voltage needed toactivate the switch. As long as power is supplied to the operationalamplifier, the comparison between the negative input and the positiveinput to the amplifier is done.

In a scenario where the negative input to the amplifier is less than thepositive input, the output from the amplifier may be similar to thepositive power supply. The positive power supply may be substantiallygreater than the relative ground, creating a differential voltagebetween the output of the amplifier and the relative ground. The voltagedivider connected to the output of the amplifier may set a voltage level(depending on the ratio between the resistors of the voltage divider) atthe gate of the bypass switch high enough to activate the switch andenable the bypass circuit, step 423. Bypass may continue as long as thevoltage level at the negative input of the amplifier is lower than thereference voltage level at the positive input to the amplifier.

Reference is now made to FIG. 5 , which shows a method 500 for enablingbypass according to an embodiment. A power system may have one or morestrings of one or more power devices connected in parallel and/orseries. Each one of the power devices may be coupled to a powergenerator. Each one of the power devices may extract power from thepower generators to the common string. The common string may carry ACand/or DC current and/or voltage. Method 500 may begin at step 501,which may include sensor(s)/sensor interface(s) coupled to or housed inone of the one or more power devices sensing operational parameters ofthe power device and the power generator coupled to the power device.Operational parameters may include input voltage current and/or power tothe power device, temperature in and/or surrounding the power device,output voltage current and/or power of the power device, voltage currentand/or power in the power device, etc. The sensed values by thesensor(s)/sensor interface(s) may be provided to a controller.

The controller, in step 502, may evaluate the signal(s) received fromthe sensor(s)/sensor interface(s) and determine if the measurements arerepresentative of a safe or unsafe, functional or dysfunctionaloperating condition. If the controller determines the measurementsrepresent a safe operating condition, the controller may control thepower device to extract power from the coupled power generator and sensethe operational parameters at step 501. If the controller determines thevalues of the measured values represent an unsafe, malfunctioning orunderproduction operating condition, the controller may activate thebypass of the power device.

The bypass of the power device may be configured to short-circuit theoutputs of the power device, and/or disconnect the inputs of the powerdevice from the power generator and/or short circuit the inputs of thepower device. According to some aspects, the power device may have acommunication device configured to receive and/or send signals to otherdevices in the power system. The communication device, in step 503, mayreceive a bypass signal, or stop receiving a keep-alive signal. Thepower device may be configured to extract power and couple to the commonstring as long as long as the keep-alive signal is being received. Whenthe keep-alive signal stops or when the bypass signal is received, thecontroller may be configured to enable the bypass and/or shutdown thepower device, and go into bypass, step 504.

Enabling the bypass of the power device may include drawing power for anauxiliary power circuit configured to provide power to the bypasscircuit. The bypass circuit may include one or more switches (e.g.,MOSFETs, BJTs, IGBTs, etc.) configured to open and short circuit thebypass circuit, such as switches QB1-QB5 of FIG. 3A. According to someaspects, the auxiliary power circuit may be configured to draw powerfrom the inputs of the power device. The inputs of the power device maybe connected to a power source. According to some aspects, the powersource may output power at a level high enough to power the auxiliarypower circuit, even in a scenario where the power source is underproducing and is to be bypassed. According to some aspects, theauxiliary power circuit may be configured to draw power from the outputsof the power device. A controller may be configured to determine if todraw power from the inputs of the power device or from the outputs, step505. The controller may be configured to draw power from the inputs ofthe power device as long as the power source is outputting enough powerto provide and power the auxiliary power circuit.

In some embodiments, where the inputs to the auxiliary power circuit arecoupled to the inputs of the power device, step 505 may be followed bystep 506 a. The auxiliary power circuit may draw power needed toactivate the bypass from the inputs to the power device. The auxiliarypower circuit may include a power converter configured to output powersuitable to power the bypass circuit that may include providing power tothe switches in the bypass circuit. The power drawn from the inputs tothe power device to the auxiliary power circuit may be converted tosuitable voltage levels needed to activate the bypass circuit. Thecontroller may activate the switches of the bypass circuit according toform of current flowing into the bypass from the common string, usingthe power drawn from the auxiliary.

According to some aspects, the controller may decide to draw power fromthe outputs of the power device and not to draw power from the inputs ofthe power device, step 506 b. The bypass circuit may include a first anda second input coupled to the outputs of the power device. The bypasscircuit may further include a first output and a second output coupledto the inputs of the auxiliary power circuit. The auxiliary powercircuit may have a power converter configured to output power suitableto power the bypass circuit that may include providing power to theswitches in the bypass circuit. The bypass circuit may draw power fromthe common string and output the amount of power needed to feed theauxiliary power circuit. After receiving the amount of power needed topower the auxiliary power circuit, the controller may activate theswitches accordingly. For example, the current and voltage from thecommon string may be DC current and voltage. The controller may turnmultiple switches ON and keep multiple switches OFF depending on thedirection of the power flow. According to some aspects, the currentand/or voltage may be in an AC form and the direction of the current maybe bidirectional. The bypass circuit may be designed as a rectifierconfigured to ensure a constant direction of current on the outputs ofthe bypass circuit. The controller may switch the switches in the bypasscircuit ON and OFF at a rate that may be proportional to the rate of thecurrent (e.g., the rate of the current may be 50 Hz and the switchingrate of the switches may be 50 Hz).

According to some aspects, the auxiliary may be coupled to the outputsof the bypass and to the inputs of the power device. The auxiliary powercircuit may have a logic block configured to output either the voltageof the input to the power device or the output of the bypass. Forexample, the logic block may be configured to perform an “OR” operationon both the voltage of the input to the power device and the output ofthe bypass, and output the greater one of the two. According to someaspects, the logic block may be configured to output the voltage of theinput to the power device as long as the voltage is over a minimumthreshold (e.g., 0.1[V]), otherwise output the voltage of the output tothe bypass.

After drawing power to the auxiliary power circuit, step 507 includesactivating the bypass. Activating the bypass may be carried out by thecontroller by turning a switch from OFF to ON and keeping it ON as longas the bypass is enabled. The bypass may be enabled as long as anenablement signal is received, a disable signal has not been receivedand/or a keep-alive signal has not been received.

Reference is now made to FIG. 6A, which shows an implementation of abypass circuit 115, according to aspects included in the disclosureherein. Coupling circuit 120 may include coupling the gate (g) of switchBP1 (of FIG. 1G) to cathode of diode D3 and a first end of resistor R4.The anode of diode D3 may couple to the cathode of diode D1, a first endof capacitor C3 and the gate (g) of switch Q8. A second end of resistorR4 may couple to a second end of capacitor C3 and terminal B. The secondend of capacitor C3 may couple to a first end of inductor L3 and asecond end of inductor L3 may couple to the anode of diode D1. The drain(d) of switch BP1 may couple to the cathode of diode PD1 at terminal Ato give a return connection RET1. The anode of diode PD1 may couple tothe source (s) of switch BP1, the anode of diode BD2 that belongs toswitch Q8 and the source (s) of switch Q8. The drain (d) of switch Q8may couple the source (s) of switch Q9 and to a first side of resistorR3. The gate (g) of switch Q9 may be coupled to circuit 606. The cathodeof diode PD2 may be coupled to a first side of resistor R1. A secondside of resistor R1 may be coupled to the drain (d) of switch Q9 and afirst end of inductor L1 of circuit 111. Switch BP1 may be a metal oxidesemiconductor field effect transistor (MOSFET), which may include diodePD1 or which might not include a diode. Similarly switches Q6, Q7 and Q9may be MOSFETs, which include a diode like diode PD2 or which might notinclude a diode. Switch Q9 may be a junction gate field-effecttransistor (J-FET). According to some aspects, bypass circuit 115 mightnot have circuit 606, switch Q8 and resistor R1.

In circuit 111, a second end of inductor L1 may couple to the drains (d)of switches Q6 and Q7. The sources (s) of Q6 and Q7 may be coupledtogether to give a return connection RET2. A first end of resistor R2may couple between the gate of switch Q7 and the source (s) of switchQ7. The gate (g) of switch Q6 may couple to a first end of capacitor C2.A second end of capacitor C2 may couple to a first end of inductor L2and a first end of capacitor C1. A second end of inductor L2 may providereturn connection RET3. A second end of capacitor C1 may couple to thegate of switch Q2. Return connections RET1, RET2 and RET3 may coupletogether to form a return path that may be separate to terminal B at thesource(s) of switch BP1. Separation between the return path and terminalB in bypass circuit 115, along with the integration of bypass circuit115 across the input of a power device 200, may be achieved by disposingswitch Q8 and diode PD2 between terminal B and inductor L1. SwitchesBP1, Q6 and Q7 may be metal oxide semiconductor field effect transistors(MOSFETs) and switch Q9 may be a junction field effect transistor(JFET).

According to some aspects, inductors L1, L2 and L3 may be mutuallycoupled on the same magnetic core. In effect, the coupling betweeninductor L1 to L2 and then inductor L2 to L3 may provide a possiblefunction of coupling between the output of circuit 111 and couplingcircuit 120. Therefore, the output of circuit 111 across inductor L1 maybe coupled back to the input of coupling circuit 120 via the mutualinductance between inductor L1 and inductor L3 and also coupled toinductor L2 via the mutual coupling between inductor L1 and inductor L2.The mutual inductance between inductor L1 and inductor L2 and voltagesinduced into inductor L2 drive the gates (g) of switches Q6 and Q7 viathe coupling of respective capacitors C2 and C1. The mutual couplingbetween inductor L1 and inductors L2 and L3 may be such that inductorsL2 and L3 have a greater number of turns across the common magnetic corethan inductor L1 does, so the voltages induced into inductors L2 and L3are greater by virtue of the transformer equations:

$\frac{VL1}{VL2} = {\frac{NL1}{NL2}\mspace{14mu}{and}}$$\frac{VL1}{VL3} = \frac{NL1}{NL3}$

where VL1, VL2 and VL3 are the respective voltages of inductors L1, L2and L3, where NL1, NL2 and NL3 are the respective number of turns ofinductors L1, L2 and L3.

The greater voltages induced into inductors L2 and L3 by virtue of thegreater number of turns NL2 and NL3 may allow for operation of switchesBP1, Q6, and Q7, whereas without the greater voltages induced, switchesBP1, Q6 and Q7 might not be able to operate otherwise. Inductor L2 andcapacitors C1 and C2 in circuit 111 function as a Colpitts oscillator.The frequency of oscillation given by:

$f_{o} = \frac{1}{2\pi\sqrt{L_{2}\left( \frac{C_{1}C_{2}}{C_{1} + C_{2}} \right)}}$

Inductors L1, L2, L3, and capacitors C1 and C2 may be chosen so that afrequency of oscillation for circuit 111 may be between 1 and 4Kilohertz (KHz). The low frequency of oscillation of circuit 111 maytherefore, provide low losses in the switching of Q6, Q7 and Q8.Alternatively, capacitor C1 may be replaced with another inductor sothat circuit 111 may be implemented as a Hartley oscillator. Inductor L3of circuit 120 may be built on the same core as inductors L1 and L2 incircuit 111, diode D1 may be used to rectify voltages induced oninductor L3 that may be by virtue of the mutual coupling betweeninductor L3 to inductors L1 and L2 of circuit 111. The rectified pulsesmay drive the voltage (Vgs) between gate (g) and source (s) of theMOSFET of switch BP1 to turn switch BP1 ON for continuous conduction ofswitch BP1 at step 1007 (see FIG. 1H).

Connected to the gate of switch Q9 may be a second side of resistor R3and circuit 606. Circuit 606 may be coupled to the gate (g) of switch Q8by the anode of diode D4. The output of a comparator comp may be coupledto the cathode of diode D4. Comparator comp may have a reference voltageVref at the positive input to comparator comp, and Vd at the negativeinput to comparator comp. Vd may be the voltage from a power sourceand/or the voltage from the power device housing bypass circuit 115. Thepositive power supply may be coupled to a first side of resistor R5 andto the cathode of a zener diode Dz. A second side of resistor R5 may becoupled to Vs. Vs may represent the output voltage of the power sourcecoupled to the power device. The anode of diode Dz may be connected to areference point, where resistor R5 and diode Dz are configured toregulate the positive power supply. The voltage output of comparatorcomp may be configured to either turn switch Q9 ON or OFF. Whencomparator comp outputs a voltage of −Vb switch Q9 is ON and when compoutputs a positive voltage relative to Vs, depending on the value of R5,switch Q9 is OFF.

Reference is now made again to FIG. 1T with method 1000 of FIG. 1Happlied to the further details of coupling circuit 120, switch BP1 andcircuit 111 in bypass circuit 115 shown in FIG. 1G, according toillustrative embodiments. At step 1003, switch BP1 may be coupled acrossthe outputs of a power device 200 where there may be a series string ofpower device 200 outputs. Switch BP1 is not active in step 1003.

At decision step 1005, specifically a first bypass current conduction ofdiode PD1 may be an indication of power device 200 and/or power source101 not functioning correctly. Consequently, the flow of current(I_(string)) through an inactive power device 200 output may becomerestricted. As a result of restricted current flow, the voltage outputsof the other power devices 200 in the string may attempt to push thecurrent through their outputs and through the inactive power device 200output. The attempt at pushing current flow of current may be caused byan increase in voltage output of the other power device 200, which maycause diode PD1 to become forward biased so that a first bypass currentconduction of current occurs through diode PD1. Diode PD1 becomingforward bias also results in diode PD2 also being forward biased. Theforward biasing of diode PD2 allows the utilization of circuit 111 toinitiate a continuous operation of switch BP1. Detailed description ofthe operation of circuit 111 is described later on in the descriptionswhich follow.

At step 1007, circuit 111 may initiate the continuous operation ofswitch BP1. As soon as body diode PD1 conducts, Q6 and/or Q7 may be ON,and circuit 605 may maintain the continuous operation of switch BP1 sothat the MOSFET of switch BP1 is ON such that the voltage (Vds) betweendrain (d) and source (s) of switch BP1 remains low, e.g., from about 10millivolts (mV) substantially up to 200 mV. A comparison between Vds of10 mV of switch Q1 and a forward voltage drop 0.7V of a bypass diode tobypass a string current (I_(string)) of 25 Amperes gives bypass powerlosses of 0.25 Watts and 17.5 Watts, respectively. As such, operation ofswitch BP1 in bypass circuit 115 and other bypass circuit embodimentsdescribed below provide efficient bypass circuits that may allow thebypassing power sources and/or other circuit elements without incurringsignificant losses by the bypass itself. Bypassing power sources and/orother circuit elements without incurring significant losses may besignificant when compared to other ways of providing a bypass that mayinclude the use of bypass diodes, for example.

At step 1007, return connections RET1, RET2 and RET3 may couple togetherto form a return path rtn that may be a separate return path to thatprovided at terminal B at the source (s) of switch BP1. Separationbetween the return path and terminal B between coupling circuit 120 andcircuit 111 may be by switch Q9 and diode BD2. Consequently,oscillations of circuit 111 may build on the drains of switches Q6and/or Q7, while the return path for the oscillations may be provided onthe sources(s) of switches Q7 and/or Q6.

At decision step 1009, if inactive power device 200 remains inactive,then the MOSFET of switch BP1 remains ON so that switch BP1 remainsactivated at step 1007. At decision step 647, if switch BP1 remainsactivated at step 1007, power from auxiliary power circuit 207 may beisolated from being supplied to the inactive power device 200. However,when power device 200 starts to become active, for example when a panelbecomes unshaded that may be sensed by sensors/sensor interfaces 203 andmay turn switch Q8 OFF, power from auxiliary power circuit 207 may beallowed to be resupplied to the switches of power device 200 to allowthe functioning of power device 200. Both the MOSFET and body diode PD1of switch BP1 and diode PD2 at this point may become reverse biased. Thereverse bias voltages of both the MOSFET and diode PD1 of switch BP1applied to the input of circuit 111 at the anode of diode PD2 may causethe ceasing of the oscillations of circuit 111. The output oscillationsof circuit 111 ceasing when feedback to the input of switch BP1 viacoupling circuit 120 may be sufficient to cause the MOSFET of switch BP1to switch OFF, so that switch BP1 is de-activated at step 1011.Alternatively, sensors/sensor interfaces 203 under control of controller204 or some other controller may sense the reverse bias voltages of boththe MOSFET and diode BD1 of switch BP1. As a result of the reversebiases being sensed, switch BP1 may be switched OFF and power fromauxiliary power circuit 207 may be allowed to be resupplied to theswitches of power device 200 to allow power device 200 to function asnormal. The reduction of voltage applied to the gate of the MOSFET ofswitch BP1 causes the MOSFET to turn OFF. With the power devices 200functioning normally switch BP1 is now inactive (OFF) but still coupledat terminals A and B (step 1003).

Reference is now made to FIG. 6B, which shows circuit 111, and a flowchart of FIG. 1K, according to illustrative embodiments. Shown is theconnection of circuit 111 to coupling circuit 120 and circuit 606. Step1007 (see also FIG. 1H, which shows the steps prior to and after step1007) occurs if a power device 200 does not work, so that switch BP1draws the current in the series string (I_(string)) in a path around theoutput of an inactive power device 200. Circuit 111 may be the same asdescribed with regard to FIG. 1G, and may be coupled to bypass switchBP1. Switches Q6 and Q7 may be biased with resistor R2. In operation ofcircuit 111 when switch BP1 is OFF and a power device 200 is workingcorrectly at step 1011, switch Q9 and diode PD2 may block leakagecurrent through bypass switch BP1 and block reverse voltage acrossbypass switch BP1 when the voltage at terminal A may be much greaterthan the voltage at terminal B. Conversely when a power device 200 isnot working at step 1007, switch Q9 is operated by the rectified outputprovided by diode D1 so that diode PD2 is bypassed by switch Q9 whenswitch Q9 may be ON. Switch Q9 OFF during step 1007 provides a block ofleakage current through bypass switch BP1. Switch Q9 being ON mayadditionally compensate for any drop in voltage across terminals A and Bas a result of switch BP1 being turned ON and being maintained as ONduring step 1007 so as to give headroom for circuit 111 to oscillate.Switch Q9 and its operation is ignored and is to be considered to be ON,in order to simplify the following description.

In decision step 1203, if a low amount of power is being produced by apower source 101 and respective power device 200 compared to other powersources 101 and respective power devices 200 in a series string of powerdevice 200 outputs, a first bypass current conduction may therefore bethrough diode PD1. Similarly, if the power source 101 and respectivepower device 200 has a failure the first bypass current conduction mayalso be through diode BD1.

At step 1205, the first bypass current conduction may induce a voltageVL1 across inductor L1 since diode PD2 is similarly forward biased asdiode BD1. At step 637 b, bypass switch BP1 may be positively biasedwith respect to output voltage (VAB) of power device 200. Bypass switchBP1 being positively biased with respect to output voltage (VAB) ofpower device 200 may be a result of power device 200 not functioning.The first bypass current conduction to provide the bypass of currentthrough bypass switch BP1 may therefore be through diode PD1, followedby the conduction of inductor L1 via diode PD2 and then by theconduction of inductor L1 by use of switch Q6 in a first stage ofoperation of bypass switch BP1.

An example of the low amount of power may be when power sources 101 maybe photovoltaic panels that have just begun to be illuminated (e.g., atdawn) or when a photovoltaic panel may be substantially and/or partiallyshaded. Shading may reduce power generated by a power source 101 (e.g.,reducing the power generated by, for example, 20%, 50% or even close to100% of the power generated by an unshaded power source). If enoughpower may be produced by power sources 101 in decision step 637 a,circuit 605 may continue to oscillate with an initial use of switch Q6for a number of times according to the steps of 637 c-637 g describedbelow as part of the first stage of operation of switch BP1 until thesecond stage of operation where switch Q7 and/or Q6 are used. Q6 may beimplemented using a junction field effect transistor (JFET) rather thana MOSFET since a JFET compared to a MOSFET may have a lower bias inputcurrent compared to a MOSFET and a JFET may conduct between source (s)and drain (d) when the voltage between gate (g) and source (Vgs) issubstantially zero. Q6 may also be implemented using a depletion modeFET.

Following on from the first stage with the use of Q6, steps 1209, 1211,1213, 1215, and 1217 are implemented with the use of switch Q7 and/orswitch Q6 as part of a second stage of operation of switch BP1. Theprincipal of operation for both the first stage and the second stage isthat inductor L1 is mutually coupled to inductors L3 and L2 when currentflows through inductor L1. The mutual coupling is such that when currentflows through inductor L1, current flows in inductor L2 and induces avoltage VL2 into inductor L2. Voltage VL2 may charge the gate (g) ofswitches Q7 and/or switch Q6 (at step 637 c) via capacitors C1 and/orC2. The charging of the gate (g) of Q7 and/or switch Q6 may cause switchQ7 and/or switch Q6 to start to conduct current between source (s) anddrain (d) of switch Q7 and/or switch Q6 so that Q7 and/or switch Q6 isON (step 637 g) for a time period ton.

The energy induced into inductor L1 during ton may be discharged by atime constant τ[L1]τ[L1]=L1×Req

where Req may be the equivalent resistance that includes resistor R1 andthe respective resistances (Rds) between drain (d) and source (s) whenswitch Q6 and/or Q7 may be ON. The value of respective resistances (Rds)between drain (d) and source (s) when switch Q7 and/or Q6 may be ON maybe derived from manufacturer data sheets for the particular deviceschosen for switches Q7 and Q6 as part of the design of circuit 605.Discharge of inductor L1 (step 1213) may continue in decision step 1215until voltage VL2 of inductor L2 in decision step 637 f drops below thethreshold voltage of Q7 and/or switch Q6 which makes Q7 and/or switch Q6switch OFF (step 1217) for a time period toff. Q7 and/or switch Q6 drain(d) voltage then may begin to increase by the ratio:

$\frac{ton}{{toff} \times {VAB}}$

so that voltage may again increase on L2 for a time defined by a timeconstant τ[L2], after which switch Q7 and/or switch Q6 conducts again(step 1209), which may create the oscillation of circuit 111. The timeconstant τ[L2] may be given by:τ[L2]=√{square root over (L2×Ceq)}

where Ceq may be the equivalent capacitance that includes capacitors C1and C2 and the parasitic capacitances of switches Q7 and/or Q6.Parasitic capacitances of switches Q7 and/or Q6 may be derived frommanufacturer data sheets for the particular devices chosen for switchesQ7 and Q6 as part of the design of circuit 111. Parasitic capacitancesof switches Q7 and/or Q6 may or might not be a significant factor in thedesired value of time constant τ[L2]. Inductor L1 coupled to inductor L3may cause a voltage to be induced in inductor L3 when current flowsthrough inductor L1. The voltage induced into inductor L3 may berectified by diode D1. The rectified voltage of diode D1 may be appliedto the gate (g) of bypass switch BP1 via diode D3 and resistor R4, whichmay turn bypass switch BP1 to be ON (step 1007).

Reference is now made to FIG. 6C, which illustrates a power device 600according to aspects of the disclosure herein. Power device 600 may bethe same as or similar to power device 200 of FIG. 2 . According to someaspects, power device 600 may have a first input In1 and a second inputIn2 configured to input power from a power source 610 to power device600. Power device 600 may have a first output Out1 and a second outputOut2. Power device 600 may be coupled to a power system (e.g. powersystem 100) with a current (I_(string)) via outputs Out1 and Out2.According to some aspects, power device may include a full bridge 601.Full bridge 601 may include a bridge of four switches (e.g. MOSFETs)S62-S65. Full bridge 601 may be configured to transfer power from powersource 610 to outputs Out1 and Out2 (e.g., full bridge 601 may functionas an inverter). In some scenarios, bypass circuit 603 may be disabled,for example, voltage Vd of circuit 606 may be greater than Vref causingthe output voltage of comparator comp to be −Vb turning switch Q8 OFF(where Vd, Vref, circuit 606, comp, Vb and Q8 appear in FIG. 6B). In ascenario where power source 610 is producing power at a sufficient leveland power device 600 is operating correctly, the voltage of terminal A(Va) may be configured to be higher than the voltage of terminal B (Vb).

Current may flow from outputs Out1 and/or Out2 of power device 600 topower source 610 and power may flow back to outputs Out1 and/or Out2. Insome scenarios, bypass circuit 603 may be enabled by turning switch Q8of FIG. 6B ON. Switches S61-S64 of full bridge 601 may have bypassdiodes (similar to or the same as diode PD1 of switch BP1 of FIG. 6B).Current may enter power device 600 through output Out1 and/or Out2 andmay reach point A flowing through the bypass diodes of switches S62 orS63. Entering bypass circuit 603, the current may flow from terminal Ato terminal B through circuit 605, resistor R1 and switch Q8 (whichappear in FIG. 6B). Flowing from terminal A to terminal B may providepower to switch BP1 through coupling circuit 120 turning switch BP1 ONand providing a path with lower impedance than through circuit 111 ofFIG. 1G, while providing enough power through circuit 111 and couplingcircuit 120 of FIG. 6A for holding switches Q9 of FIG. 6B and BP1 ON.Current may flow from point B back to output Out1 and/or Out2 throughbypass diodes of switches S64 and/or S61. According to some aspects,power on outputs Out1 and Out2, of power device 600 may be in AC form,and power source 610 may be a DC power source. Full bridge 601 may beconfigured to convert output current from AC to DC when entering powerdevice 600, and may be configured to output power from power source 610through power device 600 and out of outputs Out1 and Out2 of powerdevice 600.

Reference is now made to FIG. 6D, which illustrates aspects of powerdevice 600. Switch BP1 of FIG. 6B may be replaced by a first switch S65and a second switch S66. Switches S65 and S66 may be the same as switchBP1. Terminal A may be coupled to the drain (d) of switch S65 andterminal B may be coupled to the drain (d) of switch S66. The source (s)of switch S65 may be coupled to the source (s) of switch S66. The gate(g) of switch S65 may be coupled to the gate (g) of switch S66 as wellas to the cathode of diode D3 and a first side of resistor R4. A secondside of resistor R4 may be coupled to the sources of switch S65 andswitch S66 as well as the second side of capacitor C3 and the first endof inductor L3. The bypass circuit of FIG. 6D may be different than thecircuit depicted in FIG. 6B in that switch BP1 of FIG. 6B is replaced byswitches S65 and S66 of FIG. 6D, and point B of FIG. 6B is attached tothe drain terminal of switch S66 of FIG. 6D instead of the sourceterminal of switch BP1 of FIG. 6B.

According to some aspects, power source 610 may function as a load aswell as a source (e.g., a battery that functions as a load when chargingand functions as a source when discharging). When power source 610 isfunctioning as a source, I_(string) may flow from terminal A to terminalB, and when power source 610 is functioning as a consumer, I_(string)may flow from terminal B to terminal A. When I_(string) is flowing fromterminal A to terminal B and bypass circuit 603 is disabled, switchesS65 and S66 may be OFF and the bypass diode of switch S65 may block thecurrent from flowing through switches S65 and S66. Switch Q8 of FIG. 6Bmay be OFF preventing current from flowing through circuit 111 of FIG.6B from terminal A to terminal B. When current I_(string) is flowingfrom terminal B to terminal A, and bypass circuit 115 is disabled,switches S65 and S66 may be OFF and the bypass diode of switch S66 mayblock current from flowing from terminal B to terminal A throughswitches S65 and S66. When bypass circuit 115 is enabled, meaning switchQ8 is turned ON current may flow from terminal A to terminal B and/orvice versa through circuit 111 and may provide power to switches S65 andS66 through coupling circuit 120 of FIG. 6A. When enough power isprovided to the gates (g) of switches S65 and S66, switches S65 and S66may turn ON and I_(string) may flow through switches S65 and S66.

Having switches S65 and S66 in series may make it easier to designcoupling circuit 120 and circuit 111 and to select the values of thecomponents for one or more reasons. One reason may be creating asymmetric circuit. When switches S65 and S66 are coupled in series, thedirection of current I_(string) might not affect the voltage values andpolarity of Va and Vb. For example, I_(string) may be flowing fromterminal B to terminal A and power source 610 may be functioning as asource. The voltage difference between Va and Vb may be determinedaccording to the operation of power device 600, e.g. 50V. In a scenariowhere power source 610 is acting as a load, the voltage differencebetween Va and Vb may be 50V with I_(string) flowing from A to B. Ifswitch BP1 of bypass circuit 115 (FIG. 1G) was not replaced withswitches S65 and S66 the voltage difference may be Va−Vb=50V when thepower source is functioning as a source and I_(string) is flowing fromterminal A to terminal B. However, when power source 610 is functioningas a load the voltage difference between Va and Vb may be substantiallythe voltage of body diode PD1 of switch BP1, which may be far lower, forexample, 0.7V. Designing bypass circuit 115 to have a constant voltagedrop between terminals A and B regardless of the direction of currentflow may make it simpler and cheaper to design a circuit designed toconvert to voltage between terminals A and B to a voltage used foroperating the bypass circuit.

Reference is now made to FIG. 7A, which shows a power system 100 d,according to one or more illustrative embodiments. A connectionconfiguration 104 c is shown connected to system power device 139 atterminals + and −. Multiple connection configurations 104 d may beconnected in parallel across terminals + and −. Connectionconfigurations 104 d may be the same as connection configuration 104 cor different from connection configurations 104 c. Connectionconfiguration 104 c may include a series connection (as shown in FIG.7A) or a parallel connection of the outputs of multiple power modules103 a. The input to each power module 103 a at terminals C+ and D− maybe connected to a respective output of a power source 101. Power source101 is shown as a photovoltaic panel. Connection configuration 104 d mayinclude a series connection of the outputs of multiple power modules 103a, where the input to power module 103 a may be from another source ofDC power such as a battery or fuel cell, or rectified AC power from anAC power source such as a wind turbine, grid, or other AC generator.

A safe voltage unit 715 may be included in one or more power modules 103a. Safe voltage units 715 may be the same as or similar to, and/or mayinclude features of bypass circuits 115, 115 a, 115 b and/or 115 cdescribed above, which may be utilized to provide a substantial shortcircuit across terminals A′ and B′.

When power modules 103 a might not include a power circuit 135 (see FIG.1B, for example) disposed between terminals C+, D− and terminals A′, B′,safe voltage units 715 effectively connect across power sources 101 andterminals C+, D− may respectively be terminals A′, B′.

The communication interfaces 129 (see FIG. 1B) of the power modules 103a may be configured to communicate with each other, and/or tocommunicate with the controllers of system power device 139 and/or load107 (e.g., using power line communications or wireless communicationmethods). Load 107 may be, for example, a battery, an alternatingcurrent (AC) grid, a DC grid, or a DC to AC inverter. The power modules103 a may also receive, according to features described below, a signal70 transmitted from system power device 139 and/or load 107. Signal 70may be, for example, a “keep alive” signal or a stop signal which mayactivate or deactivate safe voltage units 715. Signal 70 may be, forexample, a wireless signal, a wired signal (e.g., via power-linecommunications or via a separate communication wire), or an acousticsignal. Power modules 103 a and utilization of bypass circuits 115, 115a, 115 b and/or 115 c as described above may include a bypass mode forshaded panels, for example, as well as a safety feature provided by useof safe voltage unit 715 described in greater detail in the descriptionswhich follow, which consider the use of signal 70.

In the descriptions that follow, by way of a non-limiting example, powermodules 103 a, do not include power circuit 135 for DC to DC conversionfrom input terminals C+, D− to output terminals A′, B′. The non-limitingexample may include use of the other features of power module 103/103 adescribed above. For example, power modules 103 a connected to systempower device 139 may provide communication capabilities (e.g., acommunication device) and/or control of a bypass and/or safe voltageunit.

Reference is now made to FIG. 7B, which shows further details of safevoltage unit 715 which may be located and connected to a power module103 a, according to one or more illustrative embodiments. Two bypasscircuits 718 a and 718 b are shown implemented as switches S76 and S75,which may be two MOSFETs with respective body diodes. The body diodesmay be an integral part of the MOSFETs or be additionally attached.Switches S76 and S75 each may be other types of semiconductor switchesor relays that may include diodes that allow a bi-directional flow ofcurrent (AC or DC current) between terminals A′ and B′ of safe voltageunit 715.

Switches S76 and S75 are implemented by two MOSFETs, the sources (s) ofthe MOSFETs connected at terminals B of switches S76 and S75 and thedrains (d) connected to terminals A′ and B′ of safe voltage unit 715.Safe voltage unit 715 further includes an auxiliary power unit 750 thatmay provide operating power to gate drivers Gd1 and Gd2. The gatedrivers may connect respectively to gates g1 and g2 in order to makeswitches S76 and S75 turn ON or OFF. Power input to auxiliary powercircuit 162 may be power P2 from power source 101 and/or operatingpowers P1 a and P1 b. Operating powers P1 a and P1 b may be providedfrom current flowing through the body diodes of respective switches S76and S75 according to the conduction of diode PD1 that may be included ina first stage as described at step 1205 above. Turning ON of switchesS76 and S75 may be according to the first and second stages of operationof bypass 115 as described above in methods 420, 500 and 1007.Therefore, in normal operating mode, safe voltage units 715 may bepowered by the voltage across the body diodes of switches S76 and S75.The body diodes of switches S76 and S75 may be substantially the same asand may provide the same function as diode PD1 of switch BP1 describedabove. Therefore, switches S76 and S75 may be considered to be twoswitches BP1 connected in series to provide a bi-directional flow ofcurrent (AC or DC current) between terminals A′ and B′ of safe voltageunit 715. Bypass circuits 718 a and 718 b may each additionally includecircuitries of bypass circuits 115, 115 a, 115 b and/or 115 c connectedto switches S76 and S75 to provide the operating bias to switches S76and S75.

Reference is now made to FIGS. 7C and 7D, which show respective flowcharts of methods 701 and 702 applied in a power system 100 d, accordingto one or more illustrative embodiments. Method 702 shows furtherdetails of step 702 of method 701 in greater detail. Power sources 101are assumed, for illustrative purposes, to be photovoltaic panels, butmay be any suitable type of power source.

In power system 100 d, power modules 103 a might not include a powercircuit 135 disposed between terminals C+, D− and terminals A′, B′. Safevoltage units 715 effectively connect across power sources 101 andterminals C+, D− may respectively be connected to terminals A′, B′. Thestring of serially connected power sources 101 may connect across systempower device 139 (step 721), and each safe voltage unit 715 connectsacross each respective power source 101 at terminals A′ and B′ (step723). Steps 721 and 723 may be carried out during installation and/orcommissioning of a PV power system, prior to first operating the powersystem in the normal mode.

In the normal operation of power system 100 d, in step 702, a controlfunction may be provided by a controller of system power device 139 or acontroller included in safety voltage unit 715 for example. Thecontroller may establish and control the string voltages or stringcurrents Istring_(1-n) from each of the connection configurations 104c/104 d connected to system power device 139 at terminals +/−. Thecontrol function may therefore establish and/or maintain an overallstring voltage Vstring an algebraic sum of string currents Istring_(1-n)to terminals +/− of system power device 139. As such, the other featuresof power modules 103 a connected to system power device 139 (e.g.,communication interfaces, controllers and/or other features describedwith respect to FIG. 1B) may provide enablement of the control function.The other features of power modules 103 a may allow the sensing ofvoltages and currents within each of the connection configurations 104c/104 d. The other features may allow communication of data of thesensing to be sent to system power device 139. The control function maytherefore enable method 701 to be applied to safe voltage units 715utilized in power system 100 d.

During the normal operation of power system 100 d, at step 725,parameters of power system 100 d may be sensed by sensors of systempower device 139, sensors 125, and/or sensor(s)/sensor interface(s)203/305. The parameters sensed may include the voltage output by thepower sources 101, the polarities of the voltages output by powersources 101 relative to each other, the current level and the directionof string currents Istring_(1-n) in connection configurations 104 c/104d, the voltage level of connection configurations 104 c/104 d and/or thepresence or the absence of a grid or load 107 connected to the output ofsystem power device 139. The control function, in response to theparameters sensed in step 725, may establish and verify the normaloperation of power system 100 d in step 702. The normal operation ofpower system 100 d in step 702 may be verified by sending signal 70 outfrom system power device 139. Safe voltage units 715 connected acrosseach one of power sources 101 in step 723 may be OFF (step 727) in thenormal mode of operation (step 702) of operation of power system 100 d.

In the case where a power source 101 comprises a PV panel that isshaded, a safe voltage unit 715 associated with that shaded PV panel maybe switched from OFF to ON in a normal mode of operation of the powersystem, due to detection of a reverse polarity of the shaded powersource 101. The detection in the normal mode of the reverse polarity mayprovide an indication of a shaded PV panel or a discharged battery (in acase where the power source 101 is a battery). Reverse polarity of anunderperforming power source 101 compared to other performing powersources 101 in a series sting may be a cause of impeding current flow inthe series string. The cause of impeding current flow in the seriesstring may be removed by switching a respective safe voltage unit 715 ofthe underperforming power source 101 from OFF to ON. Therefore, due todynamic changes of shade and state of charge of batteries over a periodof time of operating the power system, responsive to the detection inthe normal mode of operation, a number of safe voltage units 715 may beOFF or ON in a series string.

The configuration of the control function may include calculation andselection of component values, types of components and theinterconnections of components as part of an analog circuit design ofsafe voltage unit 715. The analog circuit design may further includefeatures to enable interfacing to the controller. In the absence of thecontroller or lack of operating power for the controller, operation ofsafe voltage units 715 may be independent of the control function andthe parameters sensed in step 725. The configuration may be based onnormal operating parameters (e.g., system parameters that are presentwhen power sources 101 and/or power modules 103 a are functioningcorrectly) or to accommodate non-normal operating parameters of powersystem 100 d described above and in power systems described below. Theconfiguration may thereby be responsive to an event such as thebreakdown or failure of a power module 103 a and/or power source 101 soas to provide a bypass of the power module 103 a and/or power source101.

In this regard, the configuration with respect to safe voltage unit 715with lack of control by the controller may be considered to besubstantially activated and/or operated for most of the time. Therefore,the steps of method 701 are performed responsive to the continuouslychanging operating parameters of power system 100 d. Power for theoperation of safe voltage unit 715 may be provided from the string ofserial connected power sources 101. Power for the operation may alsocome from a partial power from module 103 a and/or power source 101,which may use power P2 for example. Power for operation may also besupplied from an auxiliary power source. Safe voltage unit 715 and theother analog bypass circuit embodiments described above when consideredas being substantially activated might not require sensors 125,controller 105, and an associated algorithm to activate safe voltageunit 715 (ON) or to de-activate safe voltage unit 715 (OFF) in method701.

Therefore, a way to enable a de-activation of safe voltage circuit 115and the other analog bypass circuit embodiments described below frombeing substantially activated most of the time is for a controller touse driver circuitry 170 to apply voltages to gates g1 and g2 ofswitches S76, S75 so that safe voltage unit 715 is OFF and/orde-activated thereby. The configuration may also give the decisionaspect of decision step 704 described below so as to be responsive to anevent such as a power module 103 a and/or power source 101 revertingback to a normal operation, where the normal operation de-activates abypass of a power module 103 a and/or power source 101.

During normal operation of power system 100 d in step 702, signal 70 issent from system power device 139 and/or load 107 to power modules 103 ain each of the connection configurations 104 c/104 d. Communicationinterfaces 129 of power modules 103 a may receive signal 70 sent fromsystem power device 139 and/or load 107. If in step 704, signal 70 isreceived by power modules 103 a, normal operation of power system 100 dcontinues in step 702 where safe voltage units 715 are OFF or opencircuit between terminals A′ and B′.

When safe voltage units 715 are OFF, or de-activated, the string currentIstring₁ may be equal to the current (Is) from the poorest performingpower source 101 and the voltage across each of terminals A′ and B′ isthe voltage of a respective power source 101. When safe voltage unit 715is ON, or activated in a bypass mode (e.g., in response to anunderperforming power source 101), the voltage from a power source 101in the bypass mode may be substantially zero because the safe voltageunit 715 may substantially short-circuit the power source. As such,string current Istring₁ (from other functioning serially connected powersource 101 outputs for example) flows from terminals B′ to A′ and thevoltage drop across terminals A′ and B′ is the voltage between drain (d)and source (s) of safe voltage unit 715 (ON), where the combined drainsource voltages Vds may be 10 mV each for example. A feature of thebypass mode as explained above is that if a power source 101 was tobecome unshaded, or power source 101 begins to function again, safevoltage unit 715 may be de-activated from ON to OFF. Activation orde-activation of safe voltage unit 715 in the bypass mode may beindependent of any sensing of parameters in power system 100 d in step725.

If in step 704, signal 70 is not received by power modules 103 a, asafety mode of operation of power system 100 d may be started in step706 by activation of some and/or all of the safe voltage units 715.Signal 70 not received by power modules 103 a may be indicative of adisconnection of at least one of the power lines that connect systempower device 139 and/or load 107 to connection configurations 104 d/04d. Alternatively the disconnection may be in the power lines within aconnection configuration 104 c/104 d which may prevent a particularconnection configuration 104 c/104 d from receiving signal 70, whilstanother connection configuration 104 c/104 d might not be disconnectedfrom system power device 139 and/or load 107 and receives signal 70. Thedisconnection may also be due to a shutdown of system power device 139and/or load 107. The disconnection may be due to an over current inconfiguration 104 c/104 d blowing an inline fuse, circuit breaker orresidual current device (RCD) in the power lines within a connectionconfiguration 104 c/104 d and/or between power device 139 and/or load107 to connection configurations 104 c/104 d. The overcurrent may causean open circuit in connectors between power lines which may also befurther cause of the disconnection.

Unsafe conditions that may prevent reception of signal 70 (due to signal70 not being transmitted in response to an unsafe condition, orinhibition of the transmission of a signal 70 due to, for example,disconnected power lines) may further include, for example, adisconnection in power system 100 d, a grid outage, a leakage current,an inverter malfunction, etc. As such, safe voltage units 715 being ON,according to method 751, may ensure safe voltage level (e.g., 0.1V, 1V,2V etc.) across power sources 101 and overall a safe voltage level ofthe string voltage Vstring. Maintaining a safe Vstring level may protectoperatives such as installers and firemen for example. In other possibleimplementations, an unsafe condition may be detected in the power systemdue to the occurrence of a signal instead of the absence of a signal,whereby the signal detected may be a result of an over-voltage orover-current condition within the power system, for example.

The safety mode of operation in step 706 may be triggered in safevoltage unit 715 in various ways. According to one feature, a stopsignal may be received by a communication device included in safevoltage unit 715, the stop signal being transmitted by a system powerdevice (e.g., system power device 139). According to a feature, safevoltage unit 715 may constantly (e.g., continuously, or at regularintervals) receive a “Keep alive” signal (e.g., from system power device139) while the system is operating properly. The signal may be wired orwireless. Upon cessation of the “Keep alive signal” (e.g., having notreceived a “Keep alive” for a period of time, such as 10 seconds), thesafe voltage unit 715 may trigger the safety mode of operation (step706) by turning switches S76 and S75 ON.

A criterion for activating at least one or more safe voltage units 715may be based on a maximum acceptable safe voltage for Vstring that maybe considered to be safe in case of a disconnection between system powerdevice 139 and/or load 107 and connection configuration 104 c/104 d. Thedisconnection may include a disconnection in the power lines within aconnection configuration 104 c/104 d and/or when a shutdown of systempower device 139 and/or load 107 occurs. By way of non-limiting example,ten power modules 103 a with outputs wired in series may be included ina configuration 104 c/104 d. Each power source 101 output may be 20volts (V) and a safe voltage for Vstring is considered to be 60V when adisconnection from and/or shutdown of system power device 139 and/orload 107 occurs. At step 706, seven of the safe voltage units 715 may beturned ON in order to ensure the safe voltage, since three of the tensafe voltage units 715 are OFF. Three of the ten safe voltage units 715being OFF by virtue of Kirchoff Voltage Law givesVstring=20V+20V+20V=60V. Step 706 may be permanently applied to ensurethe safe voltage until a reconnection of connection configuration 104c/104 d and/or startup of system power device 139 and/or load 107occurs. The reconnection of connection configuration 104 c/104 d and/orstartup of system power device 139 and/or load 107 may reestablish thenormal mode of operation in step 702.

The control algorithm of a controller located in system power device 139and/or at least one of the power modules 103 a is aware of what amaximum voltage for Vstring. The maximum voltage for Vstring may bebased system requirements for a safe voltage. Where the output voltageor the combined output voltages in parts of string are considered notsafe, the control algorithm may act to ensure a safe voltage level ateach point in the series string. The safe voltage level may be achievedby activating all of the safe voltage units 715 ON. The controlalgorithm may deem it fit to activate some of the safe voltage units 715ON to ensure the safe voltage for Vstring as shown in the numericalexample above.

Reference is now made to FIG. 7E, which shows a method 751, according toone or more illustrative embodiments. Method 751 may be applied by acontroller of power system 100 d to safe voltage units 715 utilized inpower system 100 d. As previously described, the controller may be partof system power device 139 or may be included in power modules 103 a.Activation of safe voltage units 715 may be by control of the controllerresponsive to sensing step 725 or the analog circuitry of safe voltageunits 715 working independently of the controller. Safe voltage units715 working independently may be according to descriptions above withrespect to FIGS. 1I and 1Q, which may be appropriate for very low levelsof string current that exist at dusk or dawn, for example. Activation ofsafe voltage units 715 may also be a combination of control of thecontroller responsive to sensing step 725 and the analog circuitry ofsafe voltage units 715.

Safe voltage units 715 may provide a bidirectional flow of stringcurrents Istring_(1-n) which may flow from terminal B′ to terminal A′ orfrom terminal A′ to terminal B′. By way of non-limiting example, acontrol function of a control algorithm may be provided and applied by acontroller of power device 139 where power modules 103 a do not includethe use of a power circuit 135. The control function may thereforeestablish and/or maintain string voltage Vstring or one or more of thestring currents Istring_(1-n), or the algebraic sum of string currentsto terminals +/− of system power device 139. Other features of powermodules 103 a may provide enablement of the control function. Otherfeatures of power modules 103 a may allow the sensing of voltages andcurrents within each of the connection configurations 104 c/104 d thatmay be included in step 725 and to communicate data of the sensing tosystem power device 139. The control function may therefore allow method751 to be applied to safe voltage units 715 utilized in power system 100d.

In step 725, with reference to FIG. 7A, parameters of power system 100 dmay be sensed. The parameters sensed may include the voltage levelsoutput by power sources 101, the polarities of the voltages output bypower sources 101 relative to each other, the current level and thedirection of string currents Istring_(1-n) in connection configurations104 c/104 d, the voltage level of connection configurations 104 c/104 dand/or the presence or the absence of a grid or load 107 connected tothe output of system power device 139. In general, operation of safevoltage unit 715 may provide substantially a short circuit or an opencircuit of terminals A′ and B′. The short circuit or the open circuitmay be provided by method 751 applied to bypass circuits 718 a and 718b. The short circuit may provide string currents Istring_(1-n) flow ineither direction in connection configurations 104 c/104 d.

Safe voltage unit 715 may be utilized to provide a bypass mode forcurrent flow of string current Istring₁ from terminals B′ to A′ when oneor more of the safe voltage units 715 may be activated because ofunderperformance of panels because of shade 155 for example. The bypassmode may be provided in either the normal (step 702) or safety (step706) modes of operation. Underperformance of panels may cause a reversevoltage bias of the panels (e.g., due to excessive current being forcedthrough an underperforming panel). In some cases, the reverse voltagebias may be sensed at step 725 and may be used in criteria for thecontrol algorithm of power system 100 d to decide to be in either thenormal mode of operation (step 702) or the safety mode of operation. Assuch, if a safe voltage unit 715, is in the bypass mode, flow of stringcurrent Istring₁ from terminals B′ to A′ continues. Alternatively,(e.g., where power sources 101 are batteries with associated chargingconverter connected to safe voltage units 715 for example, and thebatteries are being charged during a normal mode of operation (step 702)of operation), flow of string current Istring₁ may be from terminals A′to B′. As such, some of the safe voltage units 715 may be activated andturned ON (e.g., because of a battery becoming substantially chargedbefore other batteries), so a bypass mode included in the normal mode ofoperation (step 702) of operation may be initiated for the chargedbattery with its associated charging converter OFF to isolate thebattery such that string current Istring₁ from terminals + to −continues to charge the other batteries.

Some, most or all of the safe voltage units 715 may be activated ON in asafety mode to ensure a safe voltage level between and at each of theterminals A′ and B′ in connection configurations 104 c to reduce thelevel of the voltage between or at terminals + and − of connectionconfigurations 104 c to a safe voltage level. A controller of systempower device 139 may implement a control function to power system 100 dbased on a control algorithm run by the controller. Criteria for thecontrol algorithm of power system 100 d to enter into the safety modefrom the normal mode of operation (step 702) may include a substantiallyzero string current Istring₁ existing and/or signal 70 not beingreceived by power modules 103 a. Safe voltage units 715 activated ON bythe controller in the safety mode may cause a direction of stringcurrent Istring₁ to be from terminals A′ to B′. When safe voltage unit715 is OFF or de-activated, string current Istring₁ may be substantiallyequal to the currents (Is) output by the power sources 101.

At decision step 752, responsive to sensing step 725, the controllercarrying out it may be decided that string currents Istring_(1-n) haveto flow from terminal A′ to terminal B′ or from terminal B′ to terminalA′. A criterion for entering the safe mode form the normal mode ofoperation (step 702) may include panels not being reversed biased, asubstantially zero string current Istring₁ and/or signal 70 not beingreceived by power modules 103 a. Activation of safety unit 715 to ON maybe such that current from string current Istring₁ is flowing fromterminal A′ to terminal B′ because switch S75 is turned ON by operatingpower P2 supplied by power source 101 at step 753. Switch S75 turned ONcauses current to flow in the body diode of switch S76 whilst switch S76may be OFF in step 755. Switch S76 may be turned ON in step 755 byimplementation of method 1007 applied to switch S76, where some of thecurrent to flow in the body diode of switch S76 as power P1 a may beutilized by circuitries of bypass circuits 115, 115 a, 115 b and/or 115c which may be included in bypass circuit 718 a to turn switches S75 andS76 ON. If, in decision step 757, switch S76 is not turned ON, step 755may continue until switch S76 is ON. If in decision step 757, switch S76is turned ON. The power to drive switches S76 and S75 via gate driversGd1 and Gd2 applied to respective gates g1 and g2 may be provided bypower P1 a and/or power P2.

Similarly, in a normal mode of operation (step 702) where power sources101 are batteries being charged via converter circuit for example,decision step 752 may consider that batteries are not reverse-biased, asubstantial string current Istring₁ does exist and/or signal 70 is beingreceived by power modules 103 a. Activation of safety unit 715 to ON maybe due to a battery connected to safety unit 715 becoming charged beforeother batteries. A bypass mode included in the normal mode of operationmay therefore be initiated for the charged battery with an associatedcharging converter OFF. The associated charging converter OFF isolatesthe battery from the effect of safety unit 715 being ON. The chargedbattery is thereby bypassed, and according to steps 753-759, stringcurrent Istring₁ from terminals A′ to B′ continues to charge the otherbatteries.

At decision step 752, responsive to sensing step 725, it may be decidedby the controller carrying out method 751 (e.g., the controller ofsystem power device 139) that string currents Istring_(1-n) should flowfrom terminal B′ to terminal A′. String currents Istring_(1-n) may flowfrom terminal B′ to terminal A′ because in a normal operation mode, someof the safe voltage units 715 may be activated ON because of shade 155affecting PV panels. Shade of panels may cause a reverse bias of thepanels. The reverse bias may be sensed (e.g., by detection of a negativevoltage across a PV panel) in step 725 and may be used in criteria for acontrol algorithm of power system 100 d. Activation of safety unit 715to ON is such that current from string current ‘string) is from terminalB’ to terminal A′ because switch S76 is turned ON by operating power P2supplied by power source 101 at step 754. Switch S76 turned ON causescurrent to flow in the body diode of switch S75 whilst switch S75 may beOFF in step 756. Switch S75 may be turned ON in step 756 byimplementation of method 1007 applied to switch S75. With switch S75 ON,power P1 b may be provided as a result of some of the current to flow inthe body diode of switch S75 may be utilized by circuitries of bypasscircuits 115, 115 a, 115 b and/or 115 c. The circuitries may be includedin bypass circuit 718 b to turn switches S75 and S76 ON. If in step 758,switch S75 is not turned ON, step 756 may continue until switch S75 isON. If in step 758, switch S75 is turned ON, the power to drive switchesS76 and S75 via gate drivers Gd1 and Gd2 applied to respective gates g1and g2 may be provided by power P1 b and/or power P2.

In general, for the descriptions above and for those which follow below,power source 101 may function as a source of string currentsIstring_(1-n) that may flow from terminal A′ to terminal B′, and/or whenpower source 101 is functioning as a sink (for example when power source101 is a battery, and the battery is being charged), string currentsIstring_(1-n) may flow from terminal B′ to terminal A′ of one or moresafe voltage units. Bypass of terminals A′ and B′ may be achieved by abi-directional switch which may include switches S65 and S66 accordingthe descriptions above with respect to FIGS. 6A-6D and with respect touse of switches S76 and S75. The descriptions above with respect toFIGS. 6A-6D may be similarly utilized in safe voltage unit 715 toprovide a bi-directional switching function to provide both the safetymode and the bypass mode for both DC currents Istring_(1-n) describedabove and AC string currents Istring_(1-n) provided in the descriptionsthat follow below.

Reference is now made to FIG. 7F, which shows a block diagram of powersystem 100 e, according to one or more illustrative embodiments. Powersystem 100 e includes multiple power sources 101, which by way ofnon-limiting example may be photovoltaic panels and/or storage devicessuch as batteries. If power module 103 a includes a power circuit 135disposed between terminals C+, D− and terminals +, −, terminals A′ andB′ of safe voltage units 715 may connect across power sources 101 atterminals C+, D− or may connect across terminals +, − of power module103 a. When power modules 103 a might not include a power circuits 135,terminals A′, B′ of safe voltage units 715 may connect across powersources 101. Terminals +, − connect respectively to one side of bridgecircuits 737. Bridge circuit 737 may be the same as bridge 306 shown inFIG. 3A. The other side of bridges 736 on terminals X and Y connect in aseries string in which flows string current Istring₁. The series stringmay connect across load 107. Load 107 may be the same as system powerdevice 139 which may be connectable to a grid 760.

Bridge circuits 737 may convert the DC from power sources 101 atterminals +, − to AC at terminals X and Y directly if there is no powercircuit 135 included in power module 103 a. If there is a power circuit135 included in power module 103 a, AC may be provided to load 107and/or grid 760 from bridge circuits 737 via DC power from powercircuits 135 at terminals +, −. Where power sources 101 are batteries inneed of charge, bridge circuits 737 may convert the AC from grid 760 toDC to be provided to the batteries directly or via power circuits 135.Therefore, if power sources 101 are batteries, currents Is may bedischarged to load 107/grid 760 in one direction and may be charged fromload 107/grid 760 to the batteries in the opposite direction. In sum,bridge circuits 737 may convert the DC from power sources 101 atterminals +, − to AC to load 107 and vice versa by converting AC fromload 107/grid 760 to DC to power sources 101. Therefore, string currentIstring₁ in the above description is an alternating current (AC).

Reference is now made to FIG. 7G, which shows further circuit details ofsafety unit 715 and bridge circuit 737 that may be included in powersystem 100 e of FIG. 7F, according to one or more illustrativeembodiments. Safety unit 715, power source 101 and the connectionbetween power source 101 and power module 103 a are described as abovewith respect to FIG. 7A and FIG. 7B. With respect to bridge circuit 737,terminals +, − connect respectively to the drains (d) of switches QB4and QB3 at terminal V and the sources (s) of switches QB5 and QB2 atterminal W. Terminals X and Y of bridge circuit 737 connect respectivelyto where the source (s) of switch QB4 connects to the drain (d) ofswitch QB5 and where the source (s) of switch QB3 connects to the drain(d) of switch QB2. In operation, bridge circuit 737 may have alternatingdrives applied to the gates (g) of switch pairs QB4 and QB2 and to thegates (g) of switch pairs QB3 and QB5. The alternating drives appliedmay be pulse width modulation (PWM) so that bridge circuit 737 mayconvert DC from terminals V and W to AC on terminals X and Y and viceversa so that that bridge circuit 737 may convert DC from terminals Xand Y to AC on terminals V and W.

Reference is now made again, by way of a non-limiting example, to FIGS.7F-7G and methods 701 and 751. The non-limiting example assumes powersources 101 are photovoltaic panels supplying power to load 107 viapower modules 103 a, which may include power circuits 135 disposedbetween terminals C+, D− and terminals +, −. Safe voltage units 715 mayconnect across +, − at terminals A′, B′. The string of seriallyconnected terminals X and Y of bridge circuits 737 connect across load107.

In normal operation of power system 100 e in step 702, a controlfunction may be provided by one or more controllers connected to powermodules 103 a. A primary power module 103 a may establish communicationand control to the other secondary power modules 103 a, safety units 715and/or bridge circuits 737. The primary power module 103 a may thereforecontrol the string voltage Vstring and/or string current Istring₁applied to load 107/grid 760. The features power modules 103 a connectedto system power device 139 may provide an enablement of the controlfunction. The other features of power modules 103 a to enable thecontrol function may allow a sensing of voltages and currents of powersources 101 and the string current Istring₁. The sensing may be includedin step 725 and the enablement may further include communication of dataof the sensing to load 107/system power device 139. The control functionmay therefore allow methods 701/751 to be applied to safe voltage units715 utilized in power system 100 e.

In the normal operation of power system 100 e, in step 725 parameters ofpower system 100 e may be sensed. The parameters sensed may include thevoltage levels of the power sources 101, the polarities of power sources101 relative to each other, the current level and the directions ofstring current Istring₁, the voltage level of the string voltage Vstringor the presence or the absence of a grid 760 and/or load 107.

The control function responsive to the parameters sensed in step 725 maytherefore establish and verify the normal operation of power system 100e in step 702 by receiving signal 70 from load 107 if similar to systempower device 139. Safety units 715 connected across terminals +, − instep 723 may provide an operating bias to safety units 715 to be ON orOFF in the normal mode of operation (step 702) of power system 100 e.The operating bias may be responsive to the parameters sensed (step 725)and controlled by the control function or be independent of the controlfunction and the parameters sensed. As previously stated, the controllermay be part of system power device 139 or may be included in powermodules 103 a. Activation of safe voltage units 715 may be by control ofthe controller responsive to sensing step 725 or the analog circuitry ofsafe voltage units 715 working independently of the controller. Safevoltage units 715 working independently may be according to descriptionsabove with respect to FIGS. 1I and 1Q, which may be appropriate for verylow levels of string current that may exist at dusk or dawn, forexample. Activation of safe voltage units 715 may also be a combinationof control of the controller responsive to sensing step 725 and theanalog circuitry of safe voltage units 715.

During normal operation of power system 100 e in step 702, signal 70 issent from system power device 139 and/or load 107 to power modules 103a. Signal 70, by way of non-limiting example may be transmitted to powermodules 103 a by power line communications. Communication interfaces 129of power modules 103 a receive signal 70 sent from system power device139 and/or load 107. If in step 704, signal 70 is received by powermodules 103 a, a normal operation of power system 100 e continues instep 702. In the normal operation, safe voltage units 715 may be OFF oropen circuit between terminals A′ and B′ and bridge circuit 737 mayconvert DC from terminals V and W to AC on terminals X and Y.

When safe voltage units 715 are OFF or de-activated, the rms value of ACstring current Istring₁ may be similar to the current (Is) from thepoorest performing power source 101 and the rms AC voltage across eachof terminals X and Y similar to the voltage of a respective power source101. Included in the normal mode of operation (step 702) responsive tosensing step 725 is a situation when the current (Is) from a powersource 101 may be substantially zero. Current (Is) substantially zeromay be because of shade 155 (if power sources 101 are photovoltaicpanels for example) or the power source 101 is faulty. In either case inthe normal mode of operation terminals X and Y may need to be bypassed.Shade 155 of panels may cause a reverse bias of the panels, which may besensed in step 725 and reduced string current Istring₁ which may be usedin criteria for a control algorithm of power system 100 e to decide tobe in the normal mode of operation (step 702) and apply bypasses toterminals X and Y. With reference to FIG. 7G, in bypass of terminals Xand Y, in a one-half cycle of AC current Istring₁, switches QB4 and QB5are OFF, QB3 and QB3 are ON. Therefore, in the one-half cycle currentthrough safe voltage unit 715 (ON) is from terminal B′ to terminal A′ byapplication of steps 754-760 of method 751 at decision 752. On the otherhalf cycle of AC current Istring₁, switches QB4 and QB5 are ON, QB3 andQB5 are OFF. Current through safe voltage unit 715 (ON) is from terminalA′ to terminal B′ by application of steps 753-759 at decision 752 ofmethod 751. Auxiliary power to power the bypass of terminals X and Y assuch may be utilized from at least auxiliary power circuits 162/750.

Similarly, in the normal mode of operation (step 702) where powersources 101 are batteries being charged via charging converter circuitsfor example, sensing step 725 and decision step 752 may consider thatbatteries are not reversed biased, a substantial string current Istring₁does exist and/or signal 70 is being received by power modules 103 a.Activation of safety unit 715 to ON may be because of a battery becomingcharged before the other batteries. The battery becoming charged beforethe other batteries may initiate a bypass mode that may be included inthe normal mode of operation (step 702). The bypass mode may beinitiated for the charged battery with its associated charging converter(power module 103 a) OFF to isolate the battery from the effect ofsafety unit 715 being ON. Therefore, the charged battery is bypassed andaccording to steps of method 751 for both directions of string currentIstring₁ from terminals A′ to B′ and from terminals B′ to A′ allowscontinued charging of the other batteries.

If in step 704, signal 70 is not received by power modules 103 a, asafety mode of operation (step 706) of power system 100 e may be startedin step 706 by activation of some and/or all of the safe voltage units715. Signal 70 not received by power modules 103 a may be indicative ofa disconnection of at least one of the power lines that connect systempower device 139 and/or load 107 to the series string connection ofterminals X and Y of bridge circuits 737. Alternatively, thedisconnection may be in the power lines within the series string orbetween the series string and power device 139/load 107. Thedisconnection may be due to an over current blowing an inline fuse,circuit breaker or residual current device (RCD) in the power lineswithin the series string and/or between power device 139 and/or load 107to the series string. The overcurrent may cause an open circuit inconnectors between power lines which may also be further cause of thedisconnection.

Unsafe conditions that may not allow signal 70 to be received mayfurther include, for example, a disconnection in power system 100 e, agrid outage, a leakage current or an inverter malfunction, etc. Safevoltage units 715 being ON, according to method 751, may ensure safevoltage level (e.g., 0.1V, 1V, 2V etc.) across power sources 101,terminals A′/B′, terminals V and W to give a safe voltage level of thestring voltage Vstring. Maintaining a safe Vstring level as well as safevoltage levels across power sources 101, terminals A′/B′ and terminals Vand W may protect operatives such as installers and fireman fromelectrocution for example.

The safety mode of operation in step 706 may be triggered in safevoltage unit 715 in various ways. According to one feature, a stopsignal may be received by a communication device included in safevoltage unit 715, the stop signal being transmitted by a system powerdevice (e.g., 139)/load 107. According to a feature, safe voltage unit715 may constantly (e.g., continuously, or at regular intervals) receivea “Keep alive” signal (e.g., from system power device 139/load 107)while the system is operating properly. The signal may be wired orwireless. Upon cessation of the “Keep alive signal” (e.g., having notreceived a “Keep alive” for a period of time, such as 10 seconds), thesafe voltage unit 715 may triggered. The safety mode of operation (step706) may therefore be by activating safe voltage unit 715 ON.

A criterion for activating at least one or more safe voltage units 715may be based on a maximum acceptable safe voltage for Vstring that maybe considered to be safe in case of a disconnection, possible causes forthe disconnection are described in more detail above. By way ofnon-limiting example, if ten bridge circuits 737 with connectionterminals X and Y wired in series are connected across system powerdevice 139 and/or load 107. Each bridge circuit 737 output may be 20volts (V) rms and a safe voltage for Vstring is considered to be 60V rmswhen a disconnection from and/or shutdown of system power device 139and/or load 107 occurs. At step 706, seven of the safe voltage units 715may be turned ON in order to ensure the safe voltage, since three of theten safe voltage units 715 are OFF. Three of the ten safe voltage units715 being OFF by virtue of Kirchoff Voltage Law givesVstring=20V+20V+20V=60V rms. Step 706 may be permanently applied toensure the safe voltage until a reconnection of power sources 101, powermodules 103 a, the series string connection of terminals X and Y ofbridge circuits 737 and/or startup of system power device 139 and/orload 107 occurs. The reconnection as such may reestablish the normalmode of operation in step 702.

The control algorithm of a controller located in load 107 and/or atleast one of the power modules 103 a is aware of what a maximum voltagefor Vstring. The maximum voltage for Vstring may be based on the numberof power modules 103 a. Where the output voltage or the combined outputvoltages in parts of string are considered not safe, the controlalgorithm may ensure a safe voltage level at each point in the seriesstring. The safe voltage level may be by activating all of the safevoltage units 715 ON. Whereas the control algorithm may deem it fit toactivate some of the safe voltage units 715 ON to ensure the safevoltage for Vstring as shown in the numerical example above.

According to some aspects, ensuring power to the auxiliary power circuitmay solve one or more problems and/or provide an advantage overauxiliary power provided only when connected to the inputs to the powerdevice. For example, in a scenario where a power generator wasdisconnected from a power device, the auxiliary power circuit mayprovide an option of bypassing the disconnected portion of the stringrather than disconnecting the entire string, or by creating an opencircuit section in a string that has a danger of arcing. Another exampleof a possible advantage according to certain aspects may be providingauxiliary power at night when the PV power generator might not providesubstantial power.

According to certain aspects, the power device may test the powergenerators to determine whether they are operating in a normal state ornot, in which the testing may require auxiliary power. Providingauxiliary power may enable the ability to perform testing on one or morepower generators and bypassing one or more power generators in the samestring. It is noted that various connections are set forth betweenelements herein. These connections are described in general and, unlessspecified otherwise, may be direct or indirect; this specification isnot intended to be limiting in this respect. Further, although elementsherein are described in terms of either hardware or software, they maybe implemented in either hardware and/or software. Additionally,elements of one embodiment may be combined with elements from otherembodiments in appropriate combinations or sub combinations.

Although the subject matter has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described above.For example, in each of the embodiments described above, the absence orpresence of a signal from a device of a power system may not necessarilybe an indication of an unsafe condition, but instead may be anindication to cause the power system to enter into a safety mode ofoperation from a normal mode of operation. For example, the absence orpresence of a signal may cause the power system to enter into a safetymode (as described above), whereupon, entry of the power system into thesafety mode of operation causes safety switches to be ON to ensure avoltage level at each point in a series string of power sources of thepower system to be at or below a predetermined voltage level, therebyreducing the level of the voltage of the series string to be at or belowthe predetermined voltage level. The entering into the safety mode ofoperation may be a result of, for example, a disconnection in the seriesstring of power sources, a disconnection between the series string and apower device which the series string is connected across, an outage of agrid connected to the power device, a leakage current, a malfunction ofthe power device, a trip of a circuit breaker, a shutdown of the powerdevice, or for any other reason a user would want or need to put thesystem in the safety mode. Rather, the specific features and actsdescribed above are described as example implementations of thefollowing claims.

Various characteristics of various embodiments of the invention ashereinafter highlighted in a set of numbered claims. Thesecharacteristics are not to be interpreted as being limiting on theinvention or inventive concept, but are provided merely as ahighlighting of some characteristics of the invention as described inthe description without suggesting a particular order of importance orrelevancy of such characteristics.

The invention claimed is:
 1. A safe voltage unit comprising: a firstterminal configured to be connected to a first power source; a secondterminal configured to be connected to a second power source; and a pairof switches connected between the first terminal and the secondterminal, wherein the pair of switches comprise a first switch connectedin series with a second switch, and wherein the pair of switches areconfigured to control a flow of current through the safe voltage unit,wherein the safe voltage unit is configured to operate in at least oneof: a first mode of operation where the first switch is turned OFF andthe flow of current does not flow through the safe voltage unit; or asecond mode of operation where the first switch is turned ON and theflow of current does flow through the safe voltage unit, and wherein,when the safe voltage unit is in the second mode of operation, the firstswitch is powered by a voltage between the first terminal and the secondterminal.
 2. The safe voltage unit of claim 1, wherein, in the firstmode of operation, the flow of current flows through the first powersource.
 3. The safe voltage unit of claim 1, wherein the second terminalis further configured to be connected to the first power source.
 4. Thesafe voltage unit of claim 1, wherein the pair of switches comprise abi-directional switch.
 5. The safe voltage unit of claim 1, wherein thepair of switches comprise a pair of transistors, and the first switchcomprises a first source terminal connected to a second source terminalof the second switch.
 6. The safe voltage unit of claim 1, wherein thefirst switch comprises a first diode, wherein the second switchcomprises a second diode, and wherein the second diode is connected inan opposite direction relative to the first diode.
 7. The safe voltageunit of claim 6, wherein the first diode is configured to permit a flowof current in a first direction and block a flow of current in a seconddirection, and the second diode is configured to permit the flow ofcurrent in the second direction and block the flow of current in thefirst direction.
 8. The safe voltage unit of claim 1, wherein the safevoltage unit is connected to a bridge circuit, the bridge circuitcomprising a plurality of terminals configured to be connected to thefirst terminal and the second terminal of the safe voltage unit.
 9. Thesafe voltage unit of claim 1, wherein the first power source comprises aphotovoltaic (PV) panel.
 10. The safe voltage unit of claim 1, whereinthe first power source comprises a storage device.
 11. The safe voltageunit of claim 1, wherein the safe voltage unit is connected to a load.12. The safe voltage unit of claim 1, further comprising a controllerconfigured to control a mode of operation of the safe voltage unit. 13.The safe voltage unit of claim 1, wherein the first mode of operation isa non-bypass mode of operation and the second mode of operation is abypass mode of operation.
 14. A system comprising: a plurality of safevoltage units, wherein each safe voltage unit of the plurality of safevoltage units comprises: a first terminal configured to be connected toa respective first power source; a second terminal configured to beconnected to a respective second power source; a pair of switchesconnected between the first terminal and the second terminal, whereinthe pair of switches comprise a first switch connected in series with asecond switch, and the pair of switches are configured to control a flowof current through a corresponding safe voltage unit; wherein each safevoltage unit of the plurality of safe voltage units is configured tooperate in at least one of: a first mode of operation where the firstswitch is turned OFF and the flow of current does not flow through thecorresponding safe voltage unit; or a second mode of operation where thefirst switch is turned ON and the flow of current does flow through thecorresponding safe voltage unit, and wherein, when a safe voltage unitof the plurality of safe voltage units is in the second mode ofoperation, corresponding first switch is powered by a voltage between acorresponding first terminal and a corresponding second terminal. 15.The system of claim 14, wherein, in the first mode of operation for eachsafe voltage unit of the plurality of safe voltage units, the flow ofcurrent flows through the respective first power source.
 16. The systemof claim 14, wherein, for each safe voltage unit of the plurality ofsafe voltage units, the second terminal is configured to be connected tothe respective first power source.
 17. The system of claim 14, wherein,for each safe voltage unit of the plurality of safe voltage units, thepair of switches comprise a bi-directional switch.
 18. The system ofclaim 14, wherein each safe voltage unit of the plurality of safevoltage units is connected to a respective bridge circuit.
 19. Thesystem of claim 14, wherein at least one safe voltage unit of theplurality of safe voltage units is connected to a load.
 20. The systemof claim 14, further comprising a controller configured to control amode of operation of the plurality of safe voltage units.
 21. The systemof claim 14, wherein the first switch comprises a first diode, whereinthe second switch comprises a second diode, and wherein the second diodeis connected in an opposite direction relative to the first diode.
 22. Amethod comprising: controlling a flow of current through a pair ofswitches of a safe voltage unit, wherein the safe voltage unit isconnected to a first power source and a second power source, and whereinthe pair of switches comprise a first switch connected in series with asecond switch; turning the first switch OFF and preventing the flow ofcurrent through the safe voltage unit; turning the first switch ON andcausing the flow of current through the safe voltage unit; and poweringthe first switch using a voltage between: a first terminal of the firstswitch connected to the first power source and a second terminal of thesecond switch connected to the second power source.
 23. The method ofclaim 22, wherein the first switch comprises a first diode, wherein thesecond switch comprises a second diode, and wherein the second diode isconnected in an opposite direction relative to the first diode.